1997 ASTON MARTIN DB7 ignition

Air Conditioning
System Fault Diagnosis ^=2?
System Fault Diagnosis
Probable causes of faults can be found by comparing actual system pressures, registered on the manifold gauge set
or recovery-recharge-recycie station, and the pressure to temperature relationship graphs found on the previous

page.
The chart below shows the interpretation that may be made by this difference. The 'Normal' condition is that
which is relevant to the prevailing ambient and evaporator temperatures.
Note: If erratic or
unusual gauge movements
are experienced, check the equipment
against a
known manifold
gauge
set.

Low Side
Normal
Gauge
Normal to low
Low
Low
Low
Low
High
High
High Side Gauge
Normal
Normal
Low
Low
Low
Normal to high
Low
High
High
Fault Finding
High
Symptom
Discharge air initially cool
then warms up
As above
Discharge air slightly cool
Discharge air warm
Discharge air slightly cool or
frost build up at expansion
valve
Discharge air slightly cool
Compressor noisy
Discharge air warm and high
side pipes hot
Discharge air warm
Sweating or frost at evaporator
Diagnosis
Moisture in system
As above
HFC 134A charge low
HFC 134A charge very low
Expansion valve stuck closed
Restriction in High side of system
Defective reed valve
HFC 134A charge high or
condenser malfunction
Expansion valve stuck open
Caution:
The microprocessor is extremely sensitive
and should only
be tested
using
a
digital multimeter with no
less
than a 3.5
digit display and a
resistance
of no
less than
2 M
ohms.
The use
of any other form of multimeter will
damage the microprocessor

irreparably.
Note: Always allow time for the
servo
motors and blower motors to come to a
rest
before starting a
check.

The car should be in a workshop and the ambient
temperature
should
be
stable
e.g.
24''C
(75°F)
for at
least
30 minutes before
commencing the automatic
check.

At 24°C the
sensor
voltage is
2.972
V
± 2 mV.
The
rate of
change
is lOmVper
1
°C.

Unless
stated
otherwise,
all
checks
are carried out at the ECM
test plugs

Mode Switch: Off Ignition Switch: Aux 2
Signal Pin No.
Battery supply 1
Recirc input 9
Earth-ground 2
Earth-ground 6
Earth-ground 10
Earth-ground 38
Earth-ground 45
From mode switch 44
To mode switch 12
Voltage
n to 14v
0to2V
0 to 40mV
0 to 40mV
0 to 40mV
0 to 40mV
0 to 40mV
0 to 12V
10 to 13.3V
8-30 May 1996

^=2?
Air Conditioning
Portable Diagnostic Unit - Signal Definitions
ThefollowingsignalsaresupportedontheAir-ConditioningControlModule. For each signal. The signal name, mnemonic
and background information are detailed.
Ambient Temperature Sensor
(AMBTEMP)
Auto-Recircuiation Input
(ARECIP)
Auto-Recirculation Output
(ARECOP)
Auxiliary Battery Positive
(AUX+)
Clutch Relay Drive Output
(CLUREL)
A/CCM Pin 34 ref Pin 6
This sensor is located in the right hand blower motor. This signal is used to enable
the A/C system to compensate for changes in ambient air temperature. The output
to pin 34 is 2.732 volts at 0 degrees Celsius and changes by 0.01 volts for each
degree Celsius above or below zero.
A/CCM Pin 9 ref Pin 6
This is effectively an On/Off switch for the A/C system and forms part of the fan
control switch.
Switch Off - Pin 9 should be at ground
Switch On - Pin 9 should be at 10+ volts.
When pin 9 is at ground, pin 3 will be at 10+ volts causing the recirculation flaps
to open.
A/CCM Pin 3 ref Pin 6
This signal will cause the recirculation flaps to close. Operating conditions should

be:

A/C Off - 10+ volts at pin 3, flaps open.
Temp demand minimum - 10+ volts at pin 3, flaps open.
Defrost - 0 volts at pin 3, flaps closed.
Temp demand max - 0 volts at pin 3, flaps closed.
A/CCM Pin 1 ref Vehicle Battery -ve
This signal istheauxiliary supply to the A/CCM. Pin
1
should read battery voltage
if the ignition switch is in the auxiliary or ignition on positions. Pin
1
should read
0 volts when the ignition switch is in the Off position or in position III whilst
cranking the engine. Loss of this supply will cause total failureof the A/C system.
A/CCM Pin 20 ref Pin 6
This signal responds to the input at pin 5 (evaporator sensor). When pin 5 is
between 2.715 and 2.725 volts, pin 20 should read below 1 volt, and the
compressor clutch will be switched off. When pin 5 is between 2.735 and 2.745

volts,
pin 20 will rise to 10+ volts and the compressor will re-engage.
Centre Vent Solenoid
(CVSOL) A/CCM Pin 18 ref Pin 6
The centre vent solenoid controls the operation of the centre vent flap. The centre
vent will open to increase the cooling capabilities of the vehicle when cooling is

selected.
In all other conditions, the centre vent will be closed.
Solenoid energised: pin 18 should read 10+volts and the centre vent will be open.
Solenoid de-energised; pin 18 should read below 0.5 volts and the centre vent
should be closed.
May 1996 8-67

Air Conditioning
Portable Diagnostic Unit Signal Definitions ~3^^?
Measurement Probe
(MPROBE)
Switched Power Input
(POWIN+)
Power Output
(POWOP+)
Right Blower Feedback Voltage
(RBLOFB)
Right Blower Output Voltage
(RBLOWOP)
Measurement probe (RED) with reference to measurement probe (BLACK).
A/CCM Pin 44 ref Pin 6
Switched power-in is a signal from the control module. Unlike the unswitched
power available on pins 1 and 12, this signal is only available when the A/C is
switched on.
A/CCM Pin 12 ref vehicle battery +ve
This is the ignition power for the whole A/C system. It passes through the A/CCM
via pins 1 and 12 (and a feedback protection diode) before supplying the fan
control switch. Pin 12 should normally read battery voltage with the ignition
switch in positions I or
II.
With the ignition switch off, pin 12 should read 0 volts.
A/CCM Pin 33 ref Pin 6
The purpose of the blower feedback is to inform the control module of the present
blower speed. This enables the control module to directly monitor and control
blower motor speed. With Manual selected, the blower operates in four basic
ranges:
Low Speed
Temp Min:
Temp Med:
Temp Max:
Medium Speed
Temp Min:
Temp Med:
Temp Max:
High Speed
Pin 33 = 1±1 volt at all temperature settings
Defrost
Pin 33 = 1±1 volt at all temperature settings
pin 33 = 5±1 volt
pin 33 = 9±1volt
pin 33 = 5±1 volt
pin 33 = 2±1 volt
pin 33 = 6±1volt
pin 33 = 2±1 volt
A/CCM Pin 32 ref Pin 6
This signal is produced by the control module to drive the blower motor. The signal
can vary from 0-3 volts depending on blower motor
speed.
The higher the voltage,
the higher the blower motor speed. This signal is amplified by a simple amplifier
circuit inside the blower motor. This circuit also supplies the feedback signals to
pins 22 and 33.
Note: If
the
signal
rises
above 5 volts, then
suspect a
fault in the amplifier circuit.
8-72 May 1996

The Aston Martin Lagonda Diagnostic System
Users Guide o: "3^^?
PDU Functions
The PDU main menu provides access into the following functions:
Diagnostics
Training
Digital Multimeter
User Self Test
Diagnostics
On selecting'Diagnostics'from the main
menu,
the user will be prompted to enter the features and market specification
of the vehicle to be tested. Use of the diagnostics in each of the above areas is described later in this guide.
Diagnostics Menu - 95 Model Year
Engine
Anti-Lock Braking System
Vlenu - 97 Model Year
Engine Diagnostics
OBD II Scan Tool
Airbag
Seat Belt Pretensioner
•
•
•
•
Transmission
Engine Datalogger
Climate Control
PATS System
Climate Control
Transmission
Anti-Lock Braking System
Security
Digital Multimeter
The Digital Multimeter function provides the capabilityto measure voltage, current, resistance, frequency, pulse width,
pulse period, and duty cycle. These measurements are usually made using the PDU measurement probes. Measurements
may also be made using the module pin selection function on the Teves Mk
II
braking system and on the Air Conditioning

system.

Training
An on-screen programme is provided to train new users in the use of screen icons and in the use of the digital multi­
meter and datalogger functions.
User Self Test
In order to prove that the equpment is functioning correctly, a complete user self test is incorporated. The user is directed
to test the PDU and then to progressively connect each part of the PDU system which will be tested by the software.
Any fault identified during the test is notified to the user. If no faults are identified, the user is advised on the correct
functioning of the system.
PDU Power
Power for the PDU is supplied via an internal rechargeable battery pack which can keep the PDU operational for
approximately one hour when disconnected from the base station and the vehicle. In order to preserve PDU battery
charge, power to the screen backlight is automatically cut after five minutes of inactivity. The power ON indicator
remains lit, indicating that the PDU is in 'stand-by' mode. One touch of the screen will restore backlight power.
When connected to the base station, power is supplied to the PDU from the Electronic Module to recharge the PDU
battery pack as necessary.
On 95 MY vehicles, the Vehicle Battery Adaptor (VBA) is used to maintain PDU power.
On 97 MY vehicles, when connected via the MPA to either diagnostic socket on the vehicle, power is supplied via pin
4 (chassis ground) and pin 16 (battery power) to maintain PDU power at all times even when the vehicle ignition is
switched off.
On all model years, when connected to the air conditioning system using the VIA, the vehicle battery adaptor (VBA)
must also be used to maintain PDU power.
9-28 September 1996

The Aston Martin Lagonda Diagnostic System
Users Guide "^7
Establishing Communications
when cable connections are completed, switch on the
vehicle ignition. The electronic control units will 'wake

up'
and communication between the selected control unit
and the PDU will be established.
As communication
is
established with the selected system,
a system menu similar to that below will be displayed.
System Menu Selections
The options for each vehicle system are described in detai
I

on the following pages but menu entries fall into the
following general areas:
Security
• Datalogger
• Diagnostic Trouble Code and
Alarm History Monitor
• RF Transponder Key Learning
• Exit a
o
Datalogger
The Datalogger function is described in detail using a
worked example at the end of this PDU Users Guide.
Diagnostic Trouble Codes
This application enables the PDU to monitor selected
control module trouble codes and provides the following
functions:
• Decode and display any trouble codes logged by
the control module being monitored.
• When supported by the module, decodeand display
enhanced trouble
codes,
together with any count of
the number of occurrences
• Clear all of the trouble codes and freeze frame data
logged in the control module.
• Monitor other data such as the alarm history in this
example.
Note: The 95model year Zytek engine management
system permits clearing of individual trouble codes
selected by the technician on the PDU.
System Specific Tests
These menu entries cover special tests required to program
ortest system specificfeatures. The following are examples
of tests provided:
Engine KOEO and KOER tests
OBDII Readiness test
Output State Control test
Throttle Potentiometer track test
Ignition Key Learn Menu
Remote Transmitter Key Learn Tests
Special Functions Programming
PATS
Security
Exit
Selecting and then confirming the exit option will return
the PDU to the Main Menu.
PDU Use
In the following
pages,
the use of the PDU on each vehicle
system is described.
Engine Diagnostics
Transmission Diagnostics
Climate Control Diagnostics
Anti-Lock Brakes Diagnostics
Passive Anti-Theft (PATS) Diagnostics
Security System Diagnostics
Airbag Diagnostics
Seat Belt Pretensioner Diagnostics
After these system specific descriptions, the following
general purpose functions are described:
Datalogger
Digital Multi-Meter
Diagnostic Trouble Codes
Printing
Training
OBD II Scan Tool
User Self-Test
9-32 September 1996

^27
The Aston Martin Lagonda Diagnostic System
Users Guide
Engine Diagnostics - 97 MY
Selecting Engine Diagnostics from the Vehicle Area screen
brings up the following Engine Diagnostics Screen.
Engine Diagnostic
• Diagnostic Trouble Codes
• KOEO on Demand Self Test
• KOER on Demand Self Test
• OBDII Readiness Tests
• Output State Control
• Throttle Checks
• Exit
o
Diagnostic Trouble Codes (DTCs)
On selecting DiagnosticTrouble
Codes,
the PCM memory
will be scanned and any recorded DTCs will be decoded
and displayed.
The engine and transmission DTCs are integral to the On
Board Diagnostics (OBDII) system and are ful ly described
in the DB7 OBD II Diagnostics Manual.
Before attempting to clear the logged DTCs, record all
logged DTCs for use in subsequent fault analysis.
All logged DTCs may be cleared by selecting the EEC-V
EMS DTCs
title.
This will bring up the Clear
(C)
icon which
may be selected and confirmed to clear all logged DTCs.
Note that on clearing all logged DTCs you will also clear
the associated timers, counters and fault history files (and
extinguish the engine management warning lightfor North
American vehicles). The OBD II readines test status will
also clear down and a PI 000 (OBD II readiness test
incomplete) trouble code will be set.. A full drive cycle
(see DB7 OBD II Diagnostics Manual) must be completed
to clear the PI 000 code if required. The PI 000 code will
clear automatically after some miles of driving when all
required tests have satisfactorily completed.
Caution: If a transmission code is logged in the PCM, the
TCM DTCs must be cleared first and then clear the PCM
DTCs. If the PCM DTCs are cleared without clearing the
TCM, the TCM code will immediately reset in the PCM
when power is restored.
Key On Engine Off (KOEO) and Key On Engine
Running (KOER) On Demand Self Tests
Before either the KOEO or KOER test will run, the engine
coolant temperature must be in excess of
BO'C.
Select and
confirm either the KOEO or KOER test. If the coolant
temperature is too low, the Pre Test Engine Warm Up
screen will appear. Start the engine and run until coolant
temperature is at 80+°C.
Pre Test Engine Warm Up
Value : 41°C
80 Engine Coolant Temperature {°C)
Waiting for engine to reach
normal operating temperature
o
KOEO Test
As coolant temperature rises through the BO'C level, the
technician will be requested to turn the ignition off and
then on again. The KOEO test will then commence. Static
inputs to the PCM will be checked and any faults detected
will be recorded and displayed as DTCs. If any DTCs other
than PI 000 are logged, go to the OBD II Diagnostics
Manual and resolve the concern(s) using the OBD 11
diagnostic procedures.
KOER Test
If coolant temperature level is below 80°C, the technician
will be prompted to start and run the engine until coolant
temperature rises above 80°C. As the temperature passes
the 80°C
level,
the KOERtest will commence automatically.
If coolant temperature is above the 80°C level, the
technician wi
11
be requested to start the engine. The KOER
test will commence as the engine is started. Dynamic
inputs to the PCM will be checked and any faults detected
will be recorded and displayed as DTCs. If any DTCs other
than PI 000 are logged, go to the OBD 11 Diagnostics
Manual and resolve the problem(s) using the OBD II
diagnostic procedures.
September 1996 9-33

^
The Aston Martin Lagonda Diagnostic System
Users Guide
Signal Description
lACDTCY Idle Air Control Duty Cycle (% open)
lAT Intake Air Temperature - °C or raw input counts
lAT STAT Air Temperature - Temperature sensor failure
lAT-V Intake Air Temperature - Volts or raw counts
IGN Desired Ignition Timing - ° BTDC
INDS Input from manual lever position sensor (counts)
IPWA Injector Pulse Width in mS- Bank A (Cylinders
1
-3)
IPWB Injector Pulse Width in mS- Bank B (Cylinders 4-6)
LAMSE1 Current Short Term Fuel Trim 1, adjustment from stoich - (% of range)
LAMSE2 Current Short Term Fuel Trim 2, adjustment from stoich - (% of range)
LFC Low Speed Fan Status
LOOP Fuel Control -1 = Open Loop, 0 = Closed Loop
MAF MAX Maximum Mass Air Flow signal during normal running
MAF Raw MAF sensor output (A/D counts)
MAF STAT Mass Air Flow Meter - MAF sensor failure
MIL Mali Indicator Lamp Status -1 = Lamp On
Mis HI Cumulative misfires detected by misfire test (Hi bit).
Mis LO Cumulative misfires detected by misfire test (Lo bit).
Mis nc HI Cumulative misfires detected by a misfire test (Hi bit).
Mis nc LO Cumulative misfires detected by a misfire test.
Misi HI Cumulative misfires detected by cylinder
1
misfire test (Hi bit).
Misi LO Cumulative misfires detected by cylinder
1
misfire test (Lo bit).
Mis2 HI Cumulative misfires detected by cylinder 2 misfire test (Hi bit).
Mis2 LO Cumulative misfires detected by cylinder 2 misfire test (Lo bit).
Mis3 HI Cumulative misfires detected by cylinder 3 misfire test (Hi bit).
Mis3 LO Cumulative misfires detected by cylinder 3 misfire test (Lo bit).
Mis4 HI Cumulative misfires detected by cylinder 4 misfire test (Hi bit).
Mis4 LO Cumulative misfires detected by cylinder 4 misfire test (Lo bit).
Mis5 HI Cumulative misfires detected by cylinder 5 misfire test (Hi bit).
Mis5 LO Cumulative misfires detected by cylinder 5 misfire test (Lo bit).
Mis6 HI Cumulative misfires detected by cylinder 6 misfire test (Hi bit).
Mis6 LO Cumulative misfires detected by cylinder 6 misfire test (Lo bit).
MISF Misfire Monitor - 1 = Currently misfiring
ODCODES Total number of on-demand codes currently stored.
PGM CVS DC Purge Management Duty Cycle (% on)
PIP Profile ignition Pick-Up - PIP input level
PNP Park Neutral Position Switch
R-BIAS1 Rear bias trim (Bank 1, cylinders
1
-3)
R-BIAS2 Rear bias trim (Bank 2, cylinders 4-6)
RATCH Lowest TP reading during driving
TP MAX Maximum Throttle Potentiometer signal during normal running
TP STAT Throttle Position Sensor - TP sensor failure
TP Throttle Potentiometer - Volts or counts
TPR-V Raw counts from sensor
TQ-NET Net torque into the torque convertor
TRIP OBDII Drive Cycle Complete (except cat monitor) - 1 = Trip completed
TRIPCNT Number of Completed OBDII Trips
VS MAX Maximum Vehicle Speed signal during normal running
VS STAT Vehicle Speed Sensor mode flag
VS Vehicle Speed - MPH
WAC Wide Open Throttle A/C Cut-Off -1 = High (WOT Relay)
September 1996 9-37

The Aston Martin Lagonda Diagnostic System
Users Guide ^?
Engine Setup
- 95 MY

Two adjustments
may
beset with the aid of the PDU
on 95

MY vehicles.
• Throttle Potentiometer
• Idle Fuelling Trim
From
the 95 MY
Main Menu, make
and
confirm
the

following sequence
of
selections:
Diagnostics
/

Manual
or
Auto Transmission
/

Engine
/

Engine Setup
/

The following connection diagram will then be displayed.
Throttle Sensor Adjustment
- 95 MY

Note:
The
throttle stop
and
throttle cable adjustments
must
be
correct before setting
the
throttle potentiometer.
On completion
of the
engine setup connections
the
test
selection screen will
be
displayed.

1.
Select Throttle Potentiometer.

2.
Turn
the
ignition switch
to
position
II but do not

start
the
engine.
3. Monitorthethrottle potentiometer bargraph voltage
at fully closed
and
then
at
fully open throttle.

4.
The
throttle potentiometer voltage specifications

are:

Throttle Closed
0.57 -
0.59V

Throttle Full Open
4.00 +V

Cable Setup
Diagnostic Socket D
Engine Setup Connections
Tinrottle Position Sensor
Value
:
0.43V

570
600

Idle Voltage
(mV)
Make adjustments as
necessary

Throttle Potentiometer Voltage
5.
If
both voltages
are
either high
or low,
loosen
the

two throttle pot screws and adjust the potentiometer
until
the
specified voltages
are
achieved. Carefully
tighten both screws ensuringthat the potentiometer
does
not
move during tightening.
6.
If
either voltage
is
unstable
or if the
specified
voltages cannot
be
achieved, investigate the cause.
If
the
potentiometer
is
replaced,
set the new pot

using steps
3-5
above.
Note:
On
automatic vehicles,
the
kickdown switch
adjustment check follows the throttle
pot
adjustment.
9-38 September
1996