1994 JAGUAR XJ6 Electrical Diagnostic Manual

Electrical schematic - fault Code 45
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0
0
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588
1. Instrument Panel Fuse 6. Passenger-side Air Bag
2. Engine Compartment Fuse 7. RH Impact Sensor 3. Safing Sensor 8. LH Impact Sensor
4. Cable Reel Cassettes 9. Air Bag MIL Lamp
5. Driver-side Air Bag 10. Diagnostic Module
Fig. 1
678
X300 EDM 15.1 - 39 Issue 1 August 1994

rl Electrical
FAULT CODE 5 1
Diagnostic Monitor Internal Thermal Fuse - Intermittent Short to Ground
Normal Operation
The DM monitors voltages at various pins connected to the external circuitry as described in codes 13 and 14. On detec- tion of a short to ground in these circuits fault code 13 or 14 will be present, the MIL Lamp illuminated and the internal
thermal fuse will blow. If the short is intermittent and clears, code 51 will be present, indicating the internal thermal
fuse has blown. If the short appears again the fault memory will revert to the higher priority code 13 or 14 display. The
DM must be renewed after short circuit is located.
Possible Causes
0 Damaged harness wiring or external components.
0 Air bag deployed.
Issue 1 August 1994 15.1 - 40 X300 EDM

Electrical schematic - Fault Code 51
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1. Instrument Panel Fuse 6. Passenger-side Air Bag
2. Engine Compartment Fuse 7. RH Impact Sensor 3. Safing Sensor 8. LH Impact Sensor
4. Cable Reel Cassettes 9. Air Bag MIL Lamp
5. Driver-side Air Bag 10. Diagnostic Module
Fig.
1
X300 EDM 15.1 - 41 Issue 1 August 1994

Electrical rl
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.
Issue 1 August 1994 15.1 - 42 X300 EDM

Electrical schematic - Fault Code 52
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PO3 1
1. Instrument Panel Fuse 6. Passenger-side Air Bag
2. Engine Compartment Fuse 7. RH Impact Sensor
3. Safing Sensor 8. LH Impact Sensor
4. Cable Reel Cassettes 9. Air Bag MIL Lamp
5. Driver
-side Air Bag 10. Diagnostic
Module
Fig.
1
J86-1680
Issue 1 August 1994 X300 EDM 15.1 - 43 ~~

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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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0
Issue 1 August 1994 15.1 - 44 X300 EDM

Electrical rl
Electrical schematic - Fault Code 53
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P21
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J86-1698
1. Instrument Panel Fuse 6. Passenger-side Air Bag
7. RH Impact Sensor 2. Engine Compartment Fuse 3. Safing Sensor 8. LH Impact Sensor 4. Cable Reel Cassettes 9. Air Bag MIL Lamp 5. Driver-side Air Bag 10. Diagnostic Module
-
Fig. 1
X300 EDM 15.1 - 45 Issue 1 August 1994

Electrical
RAPID CONTINUOUS MIL LAMP FLASHING
Normal Operation
The front impact sensors each have three connections to the DM: supply, supply monitor and ground monitor. If the DM detects that both sensor supplies are disconnected and that both sensors are not grounded correctly the MIL Lamp
will flash, continually, indicating both sensor circuits are open.
Possible Causes
0 Botch front impact sensors disconnected or main wiring harness disconnected.
X300 EDM Issue 1 August 1994 15.1 - 46