1988 PONTIAC FIERO check engine

DRIVEABILITY AND EMISSIONS - FUEL INJECTION 6E-5
TERMINAL IDENTIFICATION
GROUND SERIALDATA
(SEE SPECIAL TOOLS)
DIAGNOSTIC TERMINAL
I.I.R. (IF USED) T.C.C. (IF USED)
SERVICE
ENGINE FUEL PUMP (IF USED)
SOON LAMP- IF USED
SERIAL DATA (IF USED) 3-29-86 *6S 2615-6E (SEE SPECIAL TOOLS)
Figure 2 - ALDL Connector
are stored, Code 12 will continue to flash until the
Diagnostic terminal is ungrounded.
Codes can only be obtained with the engine
stopped. Grounding the Diagnostic terminal with the
engine running gives the "field service mode".
2. Display any stored trouble codes by flashing the
"Service Engine Soon" light. Each code will be
flashed three times, then Code
12 will be flashed
again.
If a trouble code is displayed, the memory is
cleared, then the engine is run to see
if the code is
a "hard" or "intermittent" failure. If it is a "hard"
failure, a Diagnostic Code chart is used to find the
problem. If it is an intermittent failure, the charts
are not used. Diagnostic aids are usually included
on the facing page. Section
"B" also covers the
topic of "Intermittents".
A physical inspection of
the applicable system most often will resolve the
problem.
3. Energize all ECM controlled relays and solenoids
except fuel pump relay
.
4. The IAC valve on most models also moves to the
fully extended position.
Field Service Mode
If the Diagnostic terminal is grounded with the
engine running, the system will enter the Field
Service mode. In this mode, the "Service Engine
Soon" light will show whether the system is in "Open"
or
"Closed Loop".
In "Open Loop" the "Service Engine Soon" light
flashes two and one-half times per second.
In "Closed Loop", the light flashes once per second:
Also, in "Closed Loop", the light will stay OUT most of
the time
if the system is too lean. It will stay "ON"
most of the time if the system is too rich.
While the system is in Field Service Mode, the
ECM will be in the following mode:
1. New trouble codes cannot be stored in the ECM.
2. The "Closed Loop" timer is bypassed.
Clearing Trouble Codes
When the ECM sets a trouble code, the "Service
Engine Soon" light will come "ON" and a trouble code
will be stored in memory. If the problem is
intermittent, the light will go out
10 seconds after the
fault goes away. However, the trouble code will stay
in the ECM memory until the battery voltage to the
ECM is removed. Removing battery voltage for
30
seconds will clear all stored trouble codes.
Trouble Codes should be cleared after repairs have
been completed. Also, some diagnostic charts will tell
you to clear the codes before using the chart. This
allows the ECM to set the code while going thru the
chart, which will help to find the cause of the problem
more quickly.
NOTICE: To prevent ECM damage, the key must
be
"OFFn when disconnecting or
reconnecting power to
ECM (for
example battery cable,
ECM pigtail,
ECM fuse, jumper cables, etc.).
ECM Learning Ability
The ECM has a "learning" ability which allows it
to make corrections for minor variations in the fuel
system to improve driveability. If the battery is
disconnected to clear diagnostic codes, or for repair,
the "learning" process has to begin all over again.
A
change may be noted in the vehicle's performance. To
"teach" the vehicle, make sure the engine is at
operating temperature, and drive at part throttle,
with moderate acceleration and idle conditions, until
normal performance returns.
DRIVEABILITY AND EMISSIONS
SECTIONS
6E2 and 6E3 SUMMARY
The Driveability and Emissions sections are
subdivided into three sub-sections:
SECTION A: STARTING POINT AND CODE CHARTS
@ Diagnostic circuit check (Starting Point)
@ No-start and fuel system check charts
@ Code Charts
SECTION B: SYMPTOMS
e Based on driveability symptoms, when no
codes, or intermittent codes, are stored.
SECTION C: COMPONENT SYSTEMS
@ Circuit descriptions
@ On-car service
@ Functional checWDiagnosis charts

6E-6 DRIVEABILITY AND EMISSIONS - FUEL INJECTION
SECTION A
Diagnostic Procedure Summary
diagnostic charts are related to the ECM and will
determine if the ECM is working properly. This
section diagnoses the fuel system controlled by the
ECM and has charts to diagnose a circuit when the
ECM has displayed a trouble code.
The way
to approach a problem is to follow three
basic steps (shown in Figure
3):
1. We find
this out by performing the "Diagnostic Circuit
If the On-Vehicle Diagnostics aren't working, the
"Diagnostic Circuit Check" will lead you to a chart
in Section
"A" to correct the problem. If the On-
Vehicle Diagnostics are OM, the next step is:
2. Is there a Trouble Code stored? If a trouble code is
stored, go directly to the numbered code chart in
Section
"A". This will determine if the fault is
still present. If no trouble code is stored, then:
3. "Scan" Serial Data.
This involves reading the various pieces of
information available on the Serial Data Stream
with one of the tools available for that purpose.
Information on these tools and the meaning of the
various displays can be found in the succeeding
paragraphs. Expected readings can be found on
the facing page for the Diagnostic Circuit Check.
This short procedure will help lead you to repair
the problem in the least amount of time.
ALDL "SCAN" TOOLS
The AEDL connector under the dash has a variety
of information available on terminal "E" or
"M"
(depending on engine). There are several tools on the
market for reading this information.
"Scan" tools do not make the use of diagnostic
charts unnecessary. They do not tell exactly where a
problem is in a given circuit. However, with an
understanding of what each position on the equipment
measures, and knowledge of the circuit involved, the
tools can be very useful in getting information which
would be more time consuming to get with other
equipment. In some cases, "Scan" tools will provide
information that is either extremely difficult or
impossible to get with other equipment.
A "SCAN" POOL THAT DISPLAYS FAULTY DATA
SHOULD NOT BE USED AND THE PROBLEM SHOULD
BE REPORTED PO THE MANUFACTURER. THE USE OF
A FAULTY "SCAM'YVOOL CAN RESULT IN
,-d ,--,,,-,,
I SEE CHART A-2 I L----------d
l"d -------- 1 SEE CHART A-2 ----------
r-J--S...-S-- 1
: SEE CHART A-3 j ----------
Figure 3 - Diagnostic Procedure Summary
MISDIAGNOSIS
AND UNNECESSARY PARTS
REPMCEMENT.
I
Trouble Tree Charts incorporate diagnosis
procedures using an ALDL "Scan" tool where possible.
Most charts require use of a "Scan" tool when
it is
applicable. Unless instructed otherwise, code charts
in
"6E" Section "A" should not be used for diagnosis
unless the fault is still present (a "hard" failure).
Some
ECM's have three modes for transmitting
information but some only read data in the open mode.
The following information will describe each of
the three modes where applicable and the effects they
may cause.
Not all engines and ECM families will transmit
information on the Serial Data Line while in this
mode.

DRIVEABILITY AND EMISSIONS - FUEL INJECTION 6E-7
On engines that can be monitored in the open
mode, it allows certain parameters to be obtained
without changing the engine operating
characteristics. The parameters capable of being read
vary from engine family to engine family. Most
"Scan" tools are programmed so that the system will
go directly into the special mode
if the "open" mode is
not available.
ALDL (7 OK, or Special) Mode
(not used on
all engines)
In this mode, all information incorporated into a
specific
engine and ECM is obtainable. However, in
this mode the system operating characteristics are
modified as follows.
@ "Closed Loop" timers are bypassed
EST (spark) is advanced
@ IAC will control engine idle to 1000 rpm I
50 rpm (if applicable)
@ On some engines, canister purge solenoid will
be enabled
@ P/N restrict functions will be disabled.
Factory Test (Back-up or 3.9 K) Mode
(TBI, Port)
In this mode, the ECM is operating on the fuel
back-up logic and is calibrated by the Calpak or Mem-
cal. These are used to control the fuel delivery
if the
ECM fails. This mode verifies that the back-up feature
is OK. The parameters that can be read on a
"Scan"
tool in this mode are not of much use for service.
"SCAN" TOOL LIMITATIONS AND USE
The "Scan" tool allows a quick check of sensors
and switches which are inputs to the ECM. However,
on some applications the data update rate makes the
tool less effective as a voltmeter when trying to detect
an intermittent which lasts for a very short time.
However, the "Scan" tool allows one to manipulate
wiring harnesses or components under the hood while
observing the "Scan" readout. This helps in locating
intermittents with the engine not running.
intermittent Conditions
for a period of time to see if there is any change in the
readings that indicates intermittent operation.
The "Scan" tool is also a useful and quick way of
comparing operating parameters of a poorly operating
engine with a known good one. For example;
A sensor
may shift in value but not set a code. Comparing with
a known good vehicle may uncover the problem.
The "Scan" tool has the ability to save time in
diagnosis and prevent the replacement of good parts.
The key to using the "Scan" tool successfully for
diagnosis lies in the technician's ability to understand
the system he is trying to diagnose as well as an
understanding of the "Scan" tool's limitations.
Therefore, the technician should read the tool
manufacturer's operating manual to become familiar
with the operation. The following information will
describe most of the "Scan" tool positions and how
they can be helpful in diagnosis.
"SCAN" TOOL POSITIONS
The following positions may not be applicable to
all engines. See the facing page
of the diagnostic
circuit check for a particular engine to decide which
positions apply to that engine.
Mode
Check with the manufacturer to determine what
the function of this mode is. In most cases it allows the
user to place the ECM in different operating modes.
Injector Pulse Width
In this position, the reading is given in
milliseconds, which is the
"ON" time that the ECM is
commanding to the
injector(s1.
Closed LoopIOpen Loop
This position will indicate whether the engine
control system is operating in "Open Loop" or "Closed
Loop". Most systems go "Closed Loop" after a certain
amount of running time, when coolant temperature is
high enough, and the oxygen sensor becomes active.
Exhaust (RichILean Indicator)
The "Scan" tool is helpful in cases of intermittent
This indicates the O2 sensor voltage at the instant operation' The can be in and observed that the data stream is sampled. If voltage is less than
while driving the vehicle under the condition where
350 mv, the value will be lean. If above 550 mv, a rich the light comes "ON" momentarily, or the engine exhaust is indicated. driveability is poor momentarily. If the problem
seems to be related to certain areas that can be
Codes checked on the "Scan" tool, then those are the
positions that should be checked while driving the
This will display any trouble codes stored in the
vehicle. If there does not seem to be any correlation
ECM memory. between the problem and any specific circuit, the
"Scan" tool can be checked on each position, watching

6E-8 DRIVEABILITY AND EMISSIONS - FUEL INJECTION
Throttle Position Sensor (TPO) Coolant Q~erature
Values read will be the voltage as seen by the Engine
temperature is displayed in Celsius
ECM. The voltage should be the TPS specification degrees.
After the engine is started, temperature
with the throttle closed and go up to about 5 volts should
rise steadily to about
85-95" C, then stabilize
with throttle wide open
(WOT). when the thermostat opens.
Throttle Angle
Displayed, in percent, is the amount the throttle is
open. 0% is closed throttle, 100% is wide open throttle.
Oxygen (Of) Sensor
The reading will be read out in millivolts (mv)
with a range from 1 to 999 mv. If the reading is
consistently below 350 (350 mv), the fuel system
is
running lean as seen by the ECM; and if the reading is
consistently above 550 (550 mv), the system is
running rich.
In this position, information is used for assembly
verification only. PROM ID is useful only when the
vehicle
is equipped with the original ECM and PROM
or Mem-Cal.
Reading displays engine rpm. It is often useful if
extra reference pulses are suspected. A sudden high
rpm indication while at a steady throttle would
indicate electrical interference
(EMI) in the reference
circuit. This interference
is usually caused by ECM
wires too close to ignition secondary wires or an open
distributor ground circuit.
Displayed is vehicle speed, useful in checking TCC
application speed or speedometer accuracy.
MAF
This displays the amount of air passing the Mass
Air Flow
(MAF) sensor, in grams per second. It is
useful when comparing the airflow between a problem
vehicle and a known good one. Normal readings at
idle are about
4 to 8 grams. If a MAF code is set, this
reading will display the ECM default value.
This display should be the same as MAF when
there are no failures in the MAP sensor circuit. When
an MAF code is set, however, this value will not
change, and will indicate the
grn/sec that the failure
has detected.
Manifold Air Temperature (MAT) Sensor
This displays temperature of the intake manifold
air. It should read close to ambient air temperature
when the engine is cold, and rise as underhood and
engine temperatures increase.
Manifold Absolute Pressure (MAP)
The MAP sensor produces a low signal voltage
when manifold pressure is low (high vacuum) and a
high voltage when the pressure is high (low vacuum).
With the ignition "ON" and the engine stopped,
I
the manifold pressure is equal to atmospheric
pressure, and the signal voltage will be high. This 1
information is used by the ECM as an indication of
vehicle altitude and is referred to as BARO.
Comparison of this
BARO reading with a known good
vehicle with the same sensor is a good way to check
accuracy of a "suspect" sensor
*. Readings should be
the same
+ .4 volt. I
* A MAP sensor has a colored plastic insert visible I I
in the connector cavity. Sensors with the same insert I
color are identical in calibration. The harness I
I
electrical connector color also should be the same as 1 the sensor insert color.
I Vacuum (Differential Pressure) Sensor
The vacuum sensor produces a low signal voltage
when manifold vacuum is low, and a high voltage
when the vacuum is high.
With the ignition "ON" and the engine stopped,
there is no vacuum, so the voltage is low (under
1
volt). With the engine idling the vacuum is high so the
voltage is high (over
3 volts).
A vacuum sensor has a colored plastic insert
visible in the connector cavity. Sensors with the same
insert color are identical in calibration. The harness
electrical connector color also should be the same as
the sensor insert color.
This displays barometric pressure. The ECM uses
this information to adjust for altitude and pressure.
This value will vary depending on barometric
pressure and altitude. Some vehicles use a dedicated
bar0 sensor, while others take a MAP reading before
the engine is started, and at various times during
engine operation.

DRIVEABILITY AND EMISSIONS - FUEL INJECTION 6E-9
ParWNelatral Switch IAC (Idle Air Control)
The indication in this mode may vary with This system is used to control engine idle speed to
manufacturer so the type of reading for a particular the desired rpm, for different operating conditions. In
tool should be checked in the operator's manual. The this mode, the numbers will indicate the position to
important thing is that the the reading changes state which
the ECM has moved the valve pintle. The ECM
(switches) when the gear selector is moved from moves
the IAC in counts, or steps, and the number of
paridneutral to drive or reverse. these counts are displayed on a "Scan" tool.
"Trque Convertor Clutch (TCC)
In this position, the tool will indicate when the
TCC has been commanded by the ECM to turn "ONJ'.
This does not necessarily mean that the clutch was
engaged but only that the
ECM grounded the circuit
internally. The best way to determine if the clutch has
engaged is to monitor engine rpm when the TCC
comes "ON".
EGR (Duty Cycle)
The EGR system uses a valve to feed a small
amount of exhaust gas back into the intake manifold
to control formation of NO,. Like all ECM outputs, the
"Scan" tool only indicates that the ECM has
commanded the function, and does not indicate that
the function has really happened.
EGR Position
This indicates the position of the EGR pintle.
Integrator and Block Learn
Normal readings for these positions are around
128. If higher, it indicates that the ECM is adding fuel
to the base fuel calculation because the system is lean,
and if the numbers are below 128, the ECM is taking
out fuel from the base calculation because the system
is rich. The integrator gives short term corrective
action, while the block learn portion (which is a long
term correction) will only change if the integrator has
seen a condition which lasts for a calibrated period of
time.
Block Learn Multiplier (BLM) Cell - or -
Block Learn Memory (BLM)
There are up to sixteen different cells,
corresponding to ranges of rpm and engine load
(indicated by MAF or MAP signals), and other
conditions, such as
A/C or P/N switch "ON" or "OFF",
etc. The ECM learns how much adjustment is needed
in each cell, and retains it in memory, so that the
adjustment will immediately be made when the
engine operates in that cell (or
rpmlload range). This
parameter will display what cell the ECM is currently
using for the fuel calculation.
Desired RPM
This indicates the rpm to which the ECM is trying
to control the idle.
Shift Light
This displays "yes" when the ECM is commanding
the shift light to turn "ON".
PPSW (Pump Prime Switch)
This is the voltage on the fuel pump feed circuit.
The ECM will adjust fuel injector base pulse width
from this voltage value rather than from battery
voltage.
NC Request
The state of the A/C signal line to the ECM is
shown. It should read "yes" whenever the
IVC is
requested.
NC Clutch
"ON" is displayed when the ECM has commanded
the
A/C clutch "ON".
Knock Retard
This indicates the number of degrees the ECM is
retarding the electronic spark timing (EST).
Knock Signal
This displays a "yes" when knock is detected by
the ECM, and a "no" when knock is not detected.
Battery Voltage
This displays the battery voltage detected at the
ECM ignition input.
Fan
"ON" is displayed when the cooling fan has been
commanded "ON".

6E-18 DRIVEABILITY AND EMISSIONS - FUEL INJECRON
CCP (Carbon Canister Purge)
This displays "ON" when the canister purge
solenoid is commanding purge. Some display duty
cycle from
0-1008.
2nd Gear
This displays the state of the 2nd gear switch.
Yes=2nd gear applied. It remains applied in 3rd and
4th gears.
3rd Gear
This displays the state of the 3rd gear switch.
Yes= 3rd gear applied. It remains applied in 4th gear.
4th Gear
This displays the state of the 4th gear switch.
Yes
= 4th gear applied.
Fan Request
State of the AJC fan control switch is displayed. It
should read "yes" when fan is requested. Some
engines may display the state of the 2nd fan, if used.
Power Steering Pressure Switch
This reading displays the state of switch, and may
vary with the tool used, and the type of switch
installed on the vehicle. The important thing is that
the reading changes state (switches) when the
steering is moved against the stops.
Electronic Control Module (ECM)
This section describes the ECM and the
information sensors in the system. Figure
4 shows
the operating conditions which the ECM may sense
and the systems that the ECM may control. (See
specific engines to determine which are applicable
to
that engine.)
Fuel Control System
The ECM controls the aidfuel delivery to the
combustion chamber by controlling the fuel flow
through the
injector(s).
Electric Fuel Pump (In-tank)
The in-tank fuel pump is controlled by the ECM.
When ignition is turned "ON", the pump will run for 2
seconds, then stop unless the ECM is receiving
ignition pulses, as when cranking or running.
Evaporative Emission ControI
This system has a canister which stores fuel vapor
from the fuel tank. The fuel vapor is removed from the
canister and consumed in the normal combustion
process when the engine is running. This system is
used on all engines and may or may not be controlled
by the ECM.
ilectronic Spark Timing (EST)
This system is controlled by the ECM, which
controls spark advance (timing), and is used on all
engines.
SECTION B - DRIVEABILIW SYMPTOMS Electronic Spark
Control (ESC)
Always start with Section "A" "Diagnostic Circuit
Check" before proceeding to the driveability
symptoms or an emissions test failure. Section "A"
checks the ECM, which may cause the driveability
problem. A definition of each symptom is included.
This will then lead to the most probable causes of the
driveability problem.
SECTION C - COMPONENT SYSTEMS
There are many component systems that are used
to control fuel and emissions. Section
"C" introduces
each component system or control with a general
description, diagnosis, and on-vehicle service.
Each of the Section "C" diagnosis sections contain
information on how the "ScanJ' tool can be used for
diagnosing a particular component when a trouble
code has not been set. (example: Section
"Cl" under
diagnosis will explain how the "Scan" tool can be used
for diagnosis as well as what the normal readings
would be for the
ECM sensors.) This
system uses a knock sensor in connection
with the ECM to control spark timing, to allow the
engine to have maximum spark advance without
spark knock. This improves driveability and fuel
economy, but will retard spark
if detonation (spark
knock) is detected.
Air Injection Reaction (A.I.R.)
The system provides additional oxygen to the
exhaust gases to continue the combustion process.
The system also supplies additional air to the catalytic
converter under certain conditions. The A.I.R. system
is not on all engines.
Early Fuel Evaporation (EFE)
The EFE system heats the engine induction
system electrically or with exhaust gas during cold

700-R4-2 HYDRAULIC DIAGNOSIS
R - Reverse allows the vehicle to be operated in
a rearward direction.
N - Neutral allows the engine to be started and
operated without driving the vehicle. If necessary this
position may be selected if the engine must be restarted
with the vehicle moving.
D - Overdrive is used for all normal driving
conditions. It provides four gear ratios plus converter
clutch operation. Downshifts are available for safe
passing by depressing the accelerator.
D - Drive position is used for city traffic, hilly
terrain, and trailer towing. It provides three gear
ranges. Again, downshifts are available by depressing
the accelerator.
2 - Manual second is used to provide acceleration
and engine braking. This range may be selected at any
vehicle speed.
1 - Manual Lo is used to provide maximum
engine
brlking. This range may also be selected at any
vehicle speed.
DIAGNOSIS INFORMATION
ROAD TEST PROCEDURE
e Perform the road test following the sequence
given
e MPH (KPH) shift points will vary with actual
throttle position and driver habits
e Compare the results of the test with speed shift
chart information. Use these results with the
diagnosis information contained in this
Automatic Transmission Hydraulic Diagnosis
Section to evaluate the transmission.
e This test should only be performed when traffic
and road conditions permit
e Observe all traffic safety regulations
Drive and Reverse Engagement Shift Check
1. Start engine
2. Depress brake pedal
3. Move gear selector:
- "Park" (P) to "Reverse" (R)
- "Reverse" (R) to "Neutral"
(N) to "Drive" (D)
Gear selections should be immediate and
not harsh.
Upshifts and Torque Converter Clutch (TCC)
Apply (Figure
2)
With gear selector in "Overdrive" (D)
1. Accelerate using a steady increasing throttle
pressure
2. Note the shift speed point gear engagements for:
- 2nd gear
- 3rd gear
- Overdrive
3. Note the speed shift point for TCC apply. This
should occur while in third gear or overdrive. If
the apply is not noticed, refer to the Preliminary
Torque Converter Clutch Diagnosis information
contained in this section of the Service Manual.
Important
The torque converter clutch will not engage if
engine coolant has not reached a minimum
operating temperature of approximately 54°C
(1 30°F).
Part Throttle Downshift
At vehicle speeds of 40-55 MPH (64-88
KPH) quickly depressed the accelerator to
a half open position and observe:
- TCC releases
- Transmission downshift to 3rd gear
immediately
Full Throttle (Detent) Downshift
At vehicle speeds of 48-55 MPH (77-88
KPH) quickly depress the accelerator to a
wide open position and observe:
- TCC releases
- Transmission downshifts to 2nd gear
immediately
Manual Downshift
1. At vehicle speeds of 40-55 MPH (64 to 88 KPH)
release the accelerator pedal while moving the
gear selector to "Third" gear (D) and observe:
- TCC release
- Transmission downshift to 3rd gear should
be immediate
- Engine should slow vehicle down
2. Move gear selector to "Overdrive" and accelerate
to 40-45 MPH (64-72 KPH). Release the
accelerator pedal while moving the gear selector
to "Second" gear (2) and observe.
- TCC release
- Downshift to second gear should be
immediate
- Engine should slow vehicle down
3. Move gear selector to "Overdrive" (D) and
accelerate to 25 MPH (40 KPH). Release the
accelerator pedal while moving the gear selector
to "First" gear (1) and observe:
- TCC release
- Transmission downshift to 1st gear should
be immediate
- Engine should slow vehicle down
Coastdown Downshift
1. With the gear selector in "Overdrive" (D)
accelerate to 4th gear with TCC applied.
2. Release the accelerator pedal and lightly apply
the brakes to observe:
- TCC release
- Shift points for downshifts.
Manual Gear Range Selection
MANUAL THIRD (D)
1. With vehicle stopped, place gear selector in
"Third" (D) and accelerate to observe:

HYDRAULIC DIAGNOSIS 700434-3
- The first to second gear shift point
- The second to third gear shift point
MANUAL SECOND (2)
2. With vehicle stopped, place gear selector in
"Second" (2) and accelerate to observe:
- The first to second gear shift point
3. Accelerate to 25 MPH (40 KPH) and observe:
- That a second to third gear shift does not
occur
- That TCC does not engage
MANUAL FIRST (I)
1. With vehicle stopped, place gear selector in
"First" (1) and accelerate to 15 MPH (24
KPH)
and observe:
- That no uoshift occurs
- That TCC does
REVERSE
1. With
vehicle stopped, place gear selector in
"Reverse" (R) and slowly accelerate to observe
reverse gear operation.
All possible throttle positions and corresponding
MPH shift point information has not been
provided.
TRANSMISSION PRESSURE CHECK
PROCEDURE
Inspect
e Fluid level
e TV cable adjustment
e Manual linkage
e Engine mechanical, emissions, electrical and fuel
delivery systems
not engage
Install or Connect (Figure 3)
a Oil pressure gage
a Tachometer