SRS JAGUAR XJ6 1994 2.G Electrical Diagnostic Manual

FAULT CODE 44
Front Right Impact Sensor Incorrectly Mounted to Vehicle
Normal Operation
The DM monitors the resistance value between pins 20 and 3. If a resistance of greater than 2.052 is detected the MIL
Lamp will illuminate and fault code 44 will be present, indicating incorrect mounting of the RH impact sensor. Secure
connections to ground at both the sensor case and the vehicle are necessary to avoid this fault.
Possible Causes
0 Poor or dirty connection between RH impact sensor case and vehicle ground.
0 Poor or dirty termination at impact sensor internal ground.
0 Open circuit on wiring between DM pin 20 and impact sensor ground terminal.
Fault Diagnosis
1. Circuit - check
Disarm the SRS system, and disconnect the battery earth lead.
. Disconnect the DM.
Measure resistance between DM pin 20 and pin 3 (ground).
. Is the resistance greater than 2.052.
Yes - Proceed to step 2.
No - Renew DM
2. Sensor - check
. Disconnect RH impact sensor from main harness.
. Measure resistance between sensor terminal 4 and ground.
. Is the resistance greater than 2.052 7
Yes -
. Remove sensor from mountings, clean all mounting surfaces (including chassis) and refit.
. Re-test resistance and renew sensor if value is still above 2.052.
NO -
. Examine harness for broken, dirty or incorrectly seated connectors.
3. On completion.
Arm and verify SRS system.
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Electrical
FAULT CODE 45
Front Left Impact Sensor Incorrectly Mounted to Vehicle
Normal Operation
The DM monitors the resistance value between pins 21 and 3. If a resistance of greater than 2 Lamp will illuminate and fault code 45 will be present, indicating incorrect mounting of the LH
connections to ground at both the sensor case and the vehicle are necessaw to avoid this fa!
Possible Causes
0 Poor or dirty connection between LH impact sensor case and vehicle ground.
0 Poor or dirty termination at impact sensor internal ground.
0 Open circuit on wiring between DM pin 21 and impact sensor ground terminal.
Fault Diagnosis
1. Circuit -check
. Disarm the SRS system, and disconnect the battery earth lead.
. Disconnect the DM.
. Measure resistance between DM pin 21 and pin 3 (ground).
. Is the resistance greater than 2.08.
Yes - Proceed to step 2.
No - Renew DM
2. Sensor - check
. Disconnect RH impact sensor from main harness.
Measure resistance between sensor terminal 4 and ground.
. Is the resistance greater than 2.051 7
Yes -
. Remove sensor from mountings, clean all mounting surfaces (including chassis) and refit.
Re-test resistance and renew sensor if value is still above 2.0Q.
NO -
. Examine harness for broken, dirty or incorrectly seated connectors.
3. On completion.
. Arm and verify SRS system.
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!.On is detected the MIL
impact sensor. Secure
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Electrical
FAULT CODE 45
Front Left Impact Sensor Incorrectly Mounted to Vehicle
Normal Operation
The DM monitors the resistance value between pins 21 and 3. If a resistance of greater than 2.08 is detected the MIL
Lamp will illuminate and fault code 45 will be present, indicating incorrect mounting of the LH impact sensor. Secure
connections to ground at both the sensor case and the vehicle are necessaw to avoid this fault.
Possible Causes
0 Poor or dirty connection between LH impact sensor case and vehicle ground.
0 Poor or dirty termination at impact sensor internal ground.
0 Open circuit on wiring between DM pin 21 and impact sensor ground terminal.
Fault Diagnosis
1. Circuit -check
. Disarm the SRS system, and disconnect the battery earth lead.
. Disconnect the DM.
. Measure resistance between DM pin 21 and pin 3 (ground).
. Is the resistance greater than 2.08.
Yes - Proceed to step 2.
No - Renew DM
2. Sensor - check
. Disconnect RH impact sensor from main harness.
Measure resistance between sensor terminal 4 and ground.
. Is the resistance greater than 2.051 7
Yes -
. Remove sensor from mountings, clean all mounting surfaces (including chassis) and refit.
Re-test resistance and renew sensor if value is still above 2.0Q.
NO -
. Examine harness for broken, dirty or incorrectly seated connectors.
3. On completion.
. Arm and verify SRS system.
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FAULT CODE 52
Back-up Power Supply - Voltage Boost Fault
Normal Operation
The DM contains a capacitor and a voltage boost circuit to provide a back-up power supply.
The voltage boost circuit charges the capacitor to approximately
24 volts when the ignition is switched on.
The back
-up power supply is connected through a diode to pin 15 of the DM (RN). The resistance to ground is infinite
due to open circuit; the open circuit allows the capacitor to maintain its higher voltage because there is no discharge
path for the capacitor.
If the voltage on the capacitor does not reach and maintain a minimum of 23 volts, approximately 45 seconds after
ignition on, the MIL Lamp will illuminate and fault code 52 will be present.
Possible Causes
0 Resistance to ground on RN wire from pin 7 safing sensor to pin 15 DM: causing capacitor discharge.
0 Voltage boost circuit within the DM.
Fault Diagnosis
1. System verification
. Disarm the SRS system.
. Switch on the ignition, allow a time delay of 45 seconds before proceeding.
. Measure the voltage between pin 15 DM and pin 3 DM (ground).
. Is the voltage measured 24 volts k 1 volt ?
Yes - Renew DM/
No - Proceed to step 2.
2.
Short circuit -check
. Switch off the ignition.
. Disconnect the DM.
. Measure the resistance between pin 15 and pin 3 (ground) on the DM.
. Is the resistance measured greater than 100,000 ohms ?
Yes - Renew DM.
No - Proceed to step 3.
3.
Circuit resistance -check
. Disconnect the safing sensor multi-plug.
. Measure the resistance between pin 15 and pin 3 (ground) on the DM.
Yes
- Proceed to step 4.
No - Locate and rectify short to ground on RN wire from pin 15 DM, to pin 7 safing sensor.
Is
the resistance measured greater than 100,000 ohms
?
4. Safing sensor - short circuit
. Measure resistance of pin 7 safing sensor (RN) to chassis ground.
. Is the resistance measured greater than 100,000 ohms ?
Yes - Locate and rectify short to ground on YP wire from pin 23 DM, to pin 6 safing sensor.
No - Renew safing sensor.
5. On completion
. Arm and verify the SRS system.
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rl Electrical
FAULT CODE 53
Front Impact Sensor Circuits Resistance to Ground or Internal Diagnostic Monitor Failure
Normal Operation
The DM measures the voltage on pins 2,6,17 and 18. If there is any resistance to ground on any of these pins or across
the front impact sensors contacts, it will cause the diagnostic voltage on these pins to drop below normal levels. If the
DM measures voltage drop to between 5 and 10 volts, the DM senses an internal voltage regulation failure and code
53 will be present.
A direct short to ground in the front impact sensor circuits
will drop the voltage to less than 5 volts and code 14 will
be present.
!!IQ&: The DM also performs several system self-tests every ignition cycle. If any of these tests fail, fault code 53 will
be present.
Fault Diagnosis
1. System verification
. Disarm the SRS system.
. Disconnect the battery ground lead, allow one minute for DM back-up power to drain.
. Disconnect the DM.
Remove the plastic locking wedge from the grey harness multi-plug connector.
= Measure the resistance between pin 3 (ground) and the following circuits:
. Pin2(ON)
. Pin 6 (VU)
. Pin 17 (KU)
* Pin 18 (KG)
. Are all circuit readings infinite (open circuit) ?
Yes - Renew DM.
No
- Proceed to step 2.
2.
. Using schematic, identify suspect sensor and circuitry.
. Disconnect the suspect sensor.
9 Measure the resistance across the normally open contacts.
. Is the resistance reading infinite (open circuit) ?
Yes - Locate and rectify short to ground on low resistance circuit.
No - Renew front impact sensor.
Impact
sensor open circuit
- check
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15.2 INSTRUMENTS
15.2.1 Introduction
The instrument pack is a self-contained, removable unit, which incorporates all the main display gauges and warning
indicators that are used to present vehicle condition information. The instrument pack is programmed during vehicle
build, to match the vehicle's individual requirements using 'Programmable Electronic Control Units System'
(PECUS). This is achieved via the diagnostic communication line, and therefore, should be renewed like-for-like. The primary
function of the instrument display is to provide the driver with information usual to normal driving requirements. The
secondary function is to display trip computer information.
The trip computer functions are selected via the steering column stalk switch
(LH). The messages are displayed in the
following order:
Odometer
- Distance - Range - Fuel Used -Average Fuel -Average Speed - Instant Fuel - Odometer (return).
Two trip computer switches, 'Reset' and 'Odo', are incorporated into the facia switch panel.
Instrument pack information is received from sensors positioned
at various locations about the vehicle (Fig. 1, follow-
ing page) via one of the two multi-pin sockets located at the rear of the instrument pack.
Information concerning vehicle condition and operation is displayed in one of three ways:
0 Information necessary to confirm normal vehicle operation: road speed, engine speed, oil pressure, battery
condition, fuel level, coolant temperature. This information is displayed using analogue gauges.
0 Information indicating the presence of a hazard/fault condition (low oil pressure/door open etc.) or operational
action (indicator flashing / headlamp full beam 'on' etc.). This information is provided by twenty two warning
lampsltell-tales, arranged in four groups; two groups of seven at the left and right sides of the instrument pack
and two groups of four
at the bottom of the instrument pack.
0 A Liquid Crystal Display (LCD) is located at the bottom-centre of the instrument pack and is normally used to
display the odometer reading, but it can also be used to display SRS fault conditions and trip computer informa-
tion such as vehicle speed, fuel usage and distance travelled.
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15.2.4.6 Engine Coolant Level
This signal (pin 37,48-way connector) comes from the coolant level switch, mounted in the lower face of the coolant
header tank. The switch is normally in the closed position, providing
a low signal to the instrument pack, when the
coolant level is acceptable. If the coolant level drops, the switch will open, removing the low signal and illuminating
the indicator lamp.
15.2.4.7 SRS Air bag fault
The input signal (pin 45, 48 way connector) is provided by the SRS Diagnostic Module.
WARNING: REFER TO SECTION 15, SUPPLEMENTAL RESTRAINT SYSTEM, BEFORE AlTEMPTlNG ANY DIAGNOSTIC
WORK ON SYSTEMS ASSOCIATED WITH THE
SRS.
15.2.4.8 Charging Fault
Battery voltage is displayed on the gauge by measuring the ignition voltage.
The red charge warning lamp will illuminate if either the voltage is too low (below
10.5V) or too high (above 15.5V). In addition,the generator provides a low signal to the instrument pack (pin 9,48-way connector) when battery charging
is unsatisfactory.
15.2.4.9 Brake System Fault (red)
The brakesystem fault receives a signal (pin 10,4&wayconnector)from the fluid level switch located in the brake fluid
reservoir. The switch is normally in the closed position, providing a low signal to the instrument pack, when the brake
fluid level is acceptable. If the fluid level drops, the switch will open, removing the lowsignal and illuminating the indi
- cator lamp.
15.2.4.10 Park Brake (red)
Park brake warning is indicated on application of the brake, which closes a micro-switch within the park brake handle
assembly. The signal to the instrument pack (pin 17, &way connector) is low when the park brake is applied and il- luminating the indicator lamp.
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