1998 OPEL FRONTERA Back

6E–234
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0502 VSS Circuit Low Input
D06RW019
Circuit Description
The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a hall
effect circuit the interacts with the magnetic field treated
by the rotating magnet. A 12-volt operating supply for the
speed sensor hall circuit is supplied from the meter fuse.
The VSS pulses to ground the 9-volt signal sent from the
powertrain control module (PCM) on the reference circuit.
The PCM interprets vehicle speed by the number of
pulses to ground per second on the reference circuit.
Conditions for Setting the DTC
Engine is running.
Engine coolant temperature is above 60C (140F).
Engine speed is between 1800 RPM and 2500 RPM.
Throttle angle is between 10% and 40%.
Engine load is greater than 50 kPa.
MAP sensor indicates greater than 50 kPa manifold
pressure.
PCM detects no VSS signal for 12.5 seconds over a
period of 25 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P0502 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
10. To avoid backprobing the VSS and possibly
damaging a seal or terminal, the VSS output can be
tested at the point where the transmission harness
connects to the engine harness. Power and ground
are applied by jumpers to the VSS through the
connectors which are located just in front of the air
cleaner assembly. The VSS signal is monitored
with a DVM as the rear driveshaft turns. The
wheels can be turned to rotate the driveshaft, or in
2-wheels-drive vehicles the driveshaft can be turned
directly.
12. The speedometer-to-PCM VSS signal wire is
spliced to a wire leading to the cruise control
module. If a short to ground or voltage is indicated
between the PCM and speedometer, it could be on
the cruise control circuit if the vehicle is equipped
with cruise control.

6E–236
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0502 – VSS Circuit Low Input
StepNo Ye s Va l u e ( s ) Action
101. Ignition “OFF.”
2. Disconnect the MAF sensor and remove the air
cleaner assembly and filter element to gain access
to the 16-way black connector located immediately
to the rear of the left front headlamp. The connector
attaches the VSS wires from the transmission
harness to the left-side engine harness.
3. Disconnect the black 16-way connector.
4. Select a terminal adapter from kit J 35616 that can
be used with a jumper to supply B+ to the blue wire
with a yellow tracer (transmission side of the
connector).
5. Use another terminal adapter to attach a voltmeter
to the light-green wire with a w h i l e t r a c e r ( n e x t t o t h e
wire in the previous step.)
6. Disconnect the blue connector next to the black
16-way connector, and locate the black/red tracer
wire at one corner of the blue connector. The
black/red wire is the VSS ground. Use a terminal
adapter to attach a jumper to ground to the
black/red VSS ground wire at the transmission side
of the blue connector.
7. Raise the rear wheels off the ground with
transmission in neutral.
Does the DVM toggle back and forth between 0.6 V and
10 V as the wheels (and driveshaft) are rotated?
—Go to Step 11Go to Step 12
11Replace the VSS.
Is the action complete?
—Verify repair—
12Check for an open or short between the PCM and the
speedometer.
Was a problem found?
—Verify repairGo to Step 13
13Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—

6E–251 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1508 IAC System Low RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detects a condition where too low of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1508 will set,
indicating a problem with the idle control system.
Conditions for Setting the DTC
No Tech 2 test is being run.
None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.
Barometric pressure is above 75 kPa.
Engine coolant temperature (ECT) is above 50C
(120
F).
Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.
The engine has been running for at least 125 seconds.
Vehicle speed is less than 1 mph.
Canister purge duty cycle is above 10%.
Ignition voltage is between 9.5 volts and 16.7 volts.
The throttle is closed.
Engine speed is lower than desired idle.
All of the above conditions are met for 10 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P1508 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM or IAC motor – Inspect
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.
Damaged harness – Inspect the wiring for damage.
Restricted air intake system – Check for a possible
collapsed air intake duct, restricted air filter element,
or foreign objects blocking the air intake system.
Throttle body – Check for objects blocking the IAC
passage or throttle bore, excessive deposits in the IAC

6E–254
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1509 IAC System High RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detect a condition where too high of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1509 will set,
indicating a problem with the idle control system.
Conditions for Setting the DTC
No Tech 2 test is being run.
None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.
Barometric pressure is above 75 kPa.
Engine coolant temperature is above 50C (120F).
Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.
The engine has been running for at least 125 seconds.
Vehicle speed is less than 1 mph.
Canister purge duty cycle is above 10%.
Ignition voltage is between 9.5 volts and 16.7 volts.
Engine speed is lower than desired idle.
All of the above conditions are met for 5 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P1509 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM or IAC motor – Inspect
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.
Damaged harness – Inspect the wiring for damage.
Vacuum leak – Check for a condition that causes a
vacuum leak, such as disconnected or damaged
h o s e s , l e a k s a t t h e E G R v a l v e a n d t h e E G R p i p e t o t h e
intake manifold, leaks at the throttle body, faulty or
incorrectly installed PCV valve, leaks at the intake
manifold, etc.

6E–259 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1640 Driver-1-Input High Voltage
Circuit Description
Output driver modules (ODMs) are used by the
powertrain control module (PCM) to turn “ON” many of
the current-driven devices that are needed to control
various engine and transmission functions. Each ODM is
capable of controlling up to 7 separate outputs by
applying ground to the device which the PCM is
commanding “ON.”
Unlike the Quad Driver Modules (QDMs) used in prior
model years, ODMs have the capability of diagnosing
each output circuit individually. DTC P1640 set indicates
an improper voltage level has been detected on an ODM
output.
Since A/C is an option, No A/C will cause the air
conditioning clutch relay output to always fault. If a fault is
seen on the air conditioning clutch relay output, it will not
be logged as a fault until the A/C request input interrupts a
high voltage, indicating that A/C has been installed.
Conditions for Setting the DTC
Ignition “ON.”
Engine running.
No DTC 1618.
Ignition voltage is above 13.2 volts for 4 seconds.
Output voltage does not equal ignition voltage when
output is “OFF” or output voltage is not less than 1 volt
when output is “ON.”
Above conditions occur for at least 1 second.
Action Taken When the DTC Sets
The PCM will not illuminate the malfunction indicator
lamp (MIL).
The PCM will store conditions which were present
when the DTC was set as Failure Records only. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC
DTC P1640 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness – Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the PCM, turn the ignition “ON” and observe a
voltmeter connected to the suspect driver circuit at the
PCM harness connector while moving connectors and
wiring harnesses relates to the MIL. A change in
voltage will indicate the location of the fault.
Poor connection at component – Examine for
damaged connectors, unplugged connector, or
damaged terminals at the following locations:
Instrument cluster harness, canister purge solenoid,
A/C clutch relay. An open ignition feed circuit at any of
these components will cause DTC P1640 to be set.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
The following PCM pins are controlled by output driver
modules (ODMs):
A13 – “Check Engine Lamp”
A14 – SVS (”Check Trans”)
B14 – A/C Clutch
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
6. The Tech 2 Driver Module Status indicates the PCM
pin that is affected.
11. The Tech 2 may indicate “short circuit” even when
the problem is an open circuit. The cause of an
open circuit may be in the component itself-lamp,
purge, solenoid, or A/C compressor relay.
13.A short to ground on the ignition side of the
component will blow the fuse. Since the fuse was
checked in Step 4, a short to ground would be
between the affected component and the PCM.

6E–261 ENGINE DRIVEABILITY AND EMISSIONS
DTC P1640 – Driver-1-Input High Voltage
StepNo Ye s Va l u e ( s ) Action
13Repair the open circuit between the fuse and the PCM
driver terminal for the affected circuit.
Is the action complete?
—Verify repair—
141. Connect the PCM.
2. Start the engine and let it idle.
3. Backprobe the affected terminal at the PCM with a
DVM.
Was the voltage equal to the specified value?
+BGo to Step 16Go to Step 15
151. Run the engine at idle.
2. Check for battery voltage at the fuse for the affected
circuit.
Was battery voltage available at the fuse?
—Go to Step 11Go to Step 10
16Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?—Verify repair—

6E–262
ENGINE DRIVEABILITY AND EMISSIONS
Symptom Diagnosis
Preliminary Checks
Before using this section, perform the “On-Board
Diagnostic (OBD) System Check” and verify all of the
following items:
The powertrain control module (PCM) and malfunction
indicator lamp (MIL) (Service Engine Soon lamp) are
operating correctly.
There are no DTC(s) stored.
Tech 2 data is within normal operating range. Refer to
Typical Scan Data Values.
Verify the customer complaint and locate the correct
symptom in the table of contents. Perform the
procedure included in the symptom chart.
Visual/Physical Check
Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time.
This check should include the following items:
PCM grounds for cleanliness, tightness and proper
location.
Vacuum hoses for splits, kinks, and proper
connections, as shown on the “Vehicle Emission
Control Information” label. Check thoroughly for any
type of leak or restriction.
Air intake ducts for collapsed or damaged areas.
Air leaks at throttle body mounting area, mass air flow
(MAF) sensor and intake manifold sealing surfaces.
Ignition wires for cracking, hardness, and carbon
tracking.
Wiring for proper connections, pinches and cuts.
Intermittents
IMPORTANT:An intermittent problem may or may not
turn on the malfunction indicator lamp (MIL) or store a
DTC. DO NOT use the Diagnostic Trouble Code (DTC)
charts for intermittent problems. The fault must be
present to locate the problem.
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions:
Poor mating of the connector halves or a terminal not
fully seated in the connector (backed out).
Improperly formed or damaged terminal.
All connector terminals in the problem circuit should be
carefully checked for proper contact tension.
Poor terminal-to-wire connection. This requires
removing the terminal from the connector body to
check.
Road test the vehicle with a J 39200 Digital Multimeter
connected to a suspected circuit. An abnormal voltage
when the malfunction occurs is a good indication that
there is a fault in the circuit being monitored.
Use Tech 2 to help detect intermittent conditions. Tech 2s
have several features that can be used to locate anintermittent condition. Use the following feature to find
intermittent faults:
Using Tech 2’s “Freeze Frame” buffer or “Failure
Records” buffer can aid in locating an intermittent
condition. Review and record the information in the
freeze frame or failure record associated with the
intermittent DTC being diagnosed. The vehicle can be
driven within the conditions that were present when the
DTC originally set.
To check for loss of diagnostic code memory, disconnect
the MAP sensor and idle the engine until the MIL (Service
Engine Soon lamp) comes on. DTC P0107 should be
stored and kept in memory when the ignition is turned
“OFF.” If not, the PCM is faulty. When this test is
completed, make sure that you clear the DTC P0107 from
memory.
An intermittent MIL (Service Engine Soon lamp) with no
stored DTC may be caused by the following:
Ignition coil shorted to ground and arcing at ignition
wires or plugs.
MIL (Service Engine Soon lamp) wire to PCM shorted
to ground.
Poor PCM grounds. Refer to the PCM wiring
diagrams.
Check for improper installation of electrical options such
as lights, cellular phones, etc. Route ignition coil wiring
away from the ignition coils. Check all wires from the
PCM to the ignition coil for poor connections.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in
Electrical Diagnosis).
If problem has not been found, refer to
PCM Connector
Symptom
tables.

6E–267 ENGINE DRIVEABILITY AND EMISSIONS
Surges and/or Chuggles Symptom
StepNo Ye s Va l u e ( s ) Action
181. Check the exhaust system for possible restriction:
Inspect the exhaust system for damaged or
collapsed pipes.
Inspect the muffler for heat distress or possible
internal failure.
Check for a possible plugged three-way
catalytic converter by checking the exhaust
system back pressure. Refer to
Restricted
Exhaust System Check
.
2. If a problem is found, repair as necessary.
Was a problem found?
—Verify repairGo to Step 19
191. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
following:
Visual/physical inspection
Te c h 2 d a t a
Freeze Frame data/Failure Records buffer
All electrical connections within a suspected
circuit and/or system.
3. If a problem is found, repair as necessary.
Was a problem found?
—Verify repair
Contact
Te c h n i c a l
Assistance