1994 JAGUAR XJ6 ignition

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CONTINUOUS AIR BAG MIL LAMP ILLUMINATION
Inoperative Lamp Circuit or No Ignition to the Diagnostic
Module
Normal Operation
The air bag MIL Lamp is designed to illuminate for approximately six seconds when the ignition is switched 'on'; this
time has been allocated to prove the MIL Lamp operation. If, after this proving period, the DM detects faults within
the system the MIL Lamp will illuminate and 'AIR BAG' will be displayed to the driver. If the MIL Lamp remains ON constantly, for over 8 seconds after ignition switch on, a fault is present within the indicator circuit.
Poor connection, or disconnection, of the indicator harness will cause
a short between pins 4 and 5, connecting the
circuit to ground and giving constant illumination of the MIL Lamp.
Faulty operation
ofthe DM internal logic may fail to turn off the indicator control circuit and cause constant illumination
of the MIL Lamp.
Fault Diagnosis
1. DM connectors
8 Disarm the SRS system.
8 Inspect the DM connectors.
2. MIL Lamp short circuit.
8 Disconnect the DM.
8 Remove the plastic locking wedge from the grey DM connector.
Switch on the ignition.
8 If the MIL Lamp is not illuminated, go to step 3.
If the MIL Lamp is illuminated; short circuit to ground between pin 45 instrument pack to pin 4 DM (Y / W). Rectify
8 Arm and verify the SRS system.
the short circuit.
3. Shorting
bar
Is the connector shorting bar operating correctly ?
Yes -
8 Renew the DM.
Reconnect, arm and verify the SRS system.
8 Renew the plastic locking wedge.
. Reconnect, arm and verify the SRS system.
NO -
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FAULT CODE 12
Low Battery Voltage
Normal Operation
The DM monitors voltage at pin 13 which should be equal to battery voltage. If a voltage lower than 9V is detected at pin 13 the MIL Lamp will illuminate and fault code 12 will be present.
Possible Causes
Drop in battery voltage to DM pin 13 caused by:
0 Open circuit to pin 13 from battery.
0 Short circuit to ground on battery feed circuit.
0 Safing sensor feed shorted to ground.
0 Safing sensor internal short to ground.
0 Faulty charging system draining battery voltage.
Fault Oiagnosis
1. Battery voltage test
Disarm the SRS system.
8 Disconnect the DM.
8 Switch on the ignition.
Measure the voltage between DM connector pin 13 (+ve) and pin 3(-ve).
If battery voltage is present at pin 13, renew the DM.
8 Arm and verify the SRS system.
8 If battery voltage is not present, go to step 2.
2.
Fusecheck
8 Check fuse 17 in the RH fuse-box.
If the fuse has blown, check for short circuit to ground between fuse and pin 13 DM connector.
8 Renew the fuse, go to step 3.
8 If the fuse has not blown, check for open circuit between battery positive terminal and pin 13 DM connector.
3. Short circuit check
* Switch off the ignition.
8 Connect the DM.
8 Has the fuse blown 1
Yes -
= Short circuit to ground from pin 15 DM (R/ W) to pin 3 safing sensor, or from pin 23 DM (Y / P) to pin 6 safing sensor.
8 Intermittent short circuit to ground; check wire (R / W) from pin 15 DM to pin 3 safing sensor, and, wire (Y/ P) from
NO -
pin 23 DM to pin 6 safing sensor.
4. On completion
8 Renew the fuse as necessary.
8 Arm and verify the SRS system.
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FAULTCODE 13
Air Bag Shorted to Ground
Normal Operation
The DM monitors voltage level at pins 11 and 12 which varies in accordance with charging voltage. If voltage measured
at these two pins falls below 2V the MIL Lamp will illuminate and fault code 13 will be present, indicating a possible
short to ground.
During the presence of fault code 13 the DM internal thermal fuse will blow, disabling the air bag deployment circuit.
If voltage to pins 11 and 12 is restored after the fuse has blown, fault code 51, open internal fuse,
will also be present.
Fault code 13 will be present only as long as the short to ground remains.
Possible Causes
Short to ground in any of the following circuits:
0 Air bag supply wiring.
0 Air bag internal.
0 Cable reel cassette internal.
0 Safing sensor supply wiring.
0 Safing sensor internal.
Fault Diagnosis
1. Air bag(s) -short circuit
. Disarm the SRS system.
. Disconnect both air bag modules multi-plug connector.
. Switch ignition ON.
. Is fault code 13 still present ?
Yes - Proceed to step 2.
No - Proceed to step 3.
2. Cable reel cassette
-short circuit
Examine wiring and connector where cable reel cassette mates to the main harness, below the steering column.
If a fault cannot be located, disconnect cable reel cassette from main harness.
. Connect air bag simulator to the main vehicle harness in place of the cable reel cassettes.
. Measure resistance between pin 11 DM and pin 3 (ground).
. Is pin 11 short circuit to ground ?
No - Proceed to fault code 51.
Yes
- Examine wiring and connections between DM, both air bags and safing sensor. Rectify faults as necessary.
If a fault is located, rectify and proceed to step 3.
3. Air bag modules
-check
. Ensure shorting bar is correctly installed to passenger-side air bag connector.
. Measure resistance between connector terminals and module casing.
If resistance value shows a short to ground, renew the module.
. If resistance shows open circuit, repeat test for driver-side module, renew as necessary.
Proceed to fault code 51 on successful diagnosis.
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FAULT CODE 23
Safing Impact Sensor Input Feed / Return Open Circuit
Normal Operation
The DM monitors the voltage on pins 15 and 23. Thevoltage on both pins should be identical. If a discrepancy between
the two measurements is detected the MIL Lamp will illuminate and fault code 23 will be present, indicating open circuit
between DM and safing sensor.
Possible Causes
Open circuit in wiring between DM pins 15 / 23 and safing sensor or internal sensor connection fault.
Fault Diagnosis
1. Voltage - check
. Disarm the SRS system.
. Measure and compare voltage at both pin 15 and pin 23, using pin 3 as a common ground.
No - Proceed to step 2
Yes - Renew DM
Turn
ignition switch to 'run' and wait 30 seconds.
Is the voltage on both pins between 23V and 26V ?
2. Resistance -check
. Disconnect safing sensor from main harness and measure resistance between YP and RN connector wires.
Is resistance value less than 2S2 ?
Yes - Examine harness wiring for open circuit. Rectify faults as necessary
No - Renew safing sensor
3. On completion
. Arm and verify the SRS system.
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FAULT CODE 24
Safing Impact Sensor Output Feed / Return Open Circuit
Normal Operation
The DM measures voltage level at pins 11 and 12 which varies in accordance with battery voltage. DM calculates what
the value at pins 11 and 12 should be from the value measured at pin 13, battery voltage. If voltage measured at pins 11 and 12 is not as expected by DM the MIL Lamp will illuminate and fault code 24 will be present, indicating a safing
sensor circuit fault.
Vbatt
9.0 9.5 1 10.0 10.5
11.0 i 11.5 12.0 12.5 I 13.0 13.5 14.0
14.5 15.0
15.5
Vpin 2.3 2.4 ~ 2.5
2.7
2.8 ~ 3.0
3.1 3.2 1 3.4 3.5 3.7 3.8 4.0
4.1
Possible Causes
0 Air bag wiring fault.
0 Safing impact sensor wiring fault.
0 Grounding of air bag /sensor circuits.
0 Intermittent battery voltage at DM pin 13.
16.0 4.3
Fault Diagnosis
1. Voltage - check
8 Disarm the SRS system.
8 Turn ignition switch OFF, then ON.
8 Measure the voltage between DM pins 11, 12 and pin 3 (ground) and compare to following table.
Are voltages within
0.5V of normal ?
Yes -
8 Check battery +ve input voltage wiring to DM pin 13.. Rectify wiring faults, if any.
8 Check fuse F17 in RH fuse-box, renew if blown.
8 Check battery, renew if necessary.
8 Renew DM if no other faults are located.
8 Proceed to step 2 if both voltages are low.
8 Proceed to step 3 if only one voltage is low.
N
O -
2. Resistance -check
8 Switch off the ignition
and disconnect battery earth lead.
8 Disconnect DM and measure resistance between pin 11 and pin 3.
8 Does resistance value indicate open circuit ?
Yes - Renew DM.
No
-Examine wiring andcomponents insafing sensor, air bag and primarysensorcircuitsforshortstoground. Rectify
faults as necessary.
3. Sensor - check
8 Switch on the ignition.
8 Disconnect safing sensor from main harness and measure resistance across connector wires YP and RN.
8 Is resistance less than 29 ?
Yes - Examine harness wiring for open circuit. Rectify faults as necessary.
No - Renew safing sensor.
4. On completion
8 Arm and verify the SRS system.
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FAULT CODE 33
Passenger-side Air BAg Circuit High Resistance or Open
Normal Operation
The DM monitors the resistance between pins 8 and 9. The value of this resistance is normally between 0.99 and 1.29. If the resistance measured exceeds 49 the MIL Lamp will illuminate and fault code 33 will be present, indicating high resistance or open circuit on the air bag circuit.
Possible Causes
0 Faulty passenger-side air bag wiring.
0 Open circuit or high resistance in passenger-side air bag.
Fault Diagnosis
1. Circuit - check
. Disarm SRS system and disconnect DM.
. Disconnect DM and remove plastic locking wedge from black DM harness connector.
Measure resistance across harness connections to passenger air bag, wires RP and KP:
. Is resistance value greater than 2.29 ?
Yes - Examine harness wiring and connections for open circuit, rectify as necessary.
No - Proceed to step 2.
2. Code verification
. Reconnect DM.
. Switch on the ignition and wait 30 seconds.
Yes
- Renew DM.
No - Proceed to step 3.
Is code 33 still present ?
3. Code 33 -check
. Switch off the ignition.
. Arm the SRS system.
. Is code 33 still present 7
Yes - Renew passenger-side air bag.
No - Examine harness wiring and connectors for intermittent open circuit.
4. On completion.
. Re-arm and verify the SRS system.
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FAULT CODE 34
Driver-side Air Bag Circuit Low Resistance or Shorted
Normal Operation
The DM monitors the resistance between pins 10 and 11. The value of this resistance is the sum of the two cable reel
cassettes and the air bag and is normally between 1.552 and 2Q. If the resistance measured is less than 0.752 the MIL Lamp will illuminate and fault code 34 will be present, indicating low resistance or short circuit on the air bag circuit.
Possible Causes
0 Poor connection of cable reel cassettes.
0 Worn cable reel cassette connectors.
0 Short circuit in cable reel cassette.
0 Poor connection of air bag harness.
0 Short circuit across air bag terminals.
Fault Diagnosis
1. Resistance - check
. Disarm the SRS system and disconnect the driver-side air bag.
rn Disconnect DM and remove plastic locking wedge from black harness connector.
. Measure resistance across harness connections to driver-side air bag, wires RP and KN.
. Does resistance value indicate open circuit.
Yes
- Proceed to step 2.
No - Proceed to step 3.
2. Diagnostic Module -check
Install air bag simulator in place of cable reel cassette at steering column base.
. Re-connect DM.
. Switch on the ignition and wait 30 seconds.
rn Is code 34 still present ?
Yes - Renew DM.
No - Examine shorting bar on driver-side air bag connector for correct operation, rectify if necessary. Renew air bag
module if shorting bar is functioning correctly.
3. Harness -check
. Measure resistance across harness connections to driver-side air bag, wires RP and KN.
. Does resistance value indicate open circuit 7
Yes -
. Examine shorting bar on cable reel cassette connector for correct operation, rectify if necessary.
. Renew cable reel cassette if shorting bar is functioning correctly.
NO -
Inspect harness wiring, cable reel cassettes and terminals for short circuit. Rectify as necessary.
4. On completion
. Arm and verify the SRS system.

FAULT CODE 35
Passenger-side Air Bag Circuit L o w Resistance or Shorted
Normal Operation
The DM monitors the resistance between pins 8 and 9. The value of this resistance is normally between 0.9Q and 1.2Q. If the resistance measured is less than 0.7Q the MIL Lamp will illuminate and fault code 35 will be present, indicating
low resistance or short circuit on the air bag circuit.
Possible Causes
0 Shorting between DM pins 8 and 9, passenger-side air bag not fitted.
0 Poor connection of air bag harness.
0 Faulty air bag harness connector.
0 Short circuit in air bag harness.
0 Short circuit across passenger-side air bag terminals.
Fault Diagnosis
8 Disarm the SRS system and disconnect the passenger-side air bag.
8 Disconnect the DM and remove the plastic locking wedge from the black harness connector.
8 Measure resistance across harness connections to passenger-side air bag, wires RP and Kf?
8 Does resistance indicate open circuit ?
Yes - Proceed to step 2.
No - Inspect harness wiring, cable reel cassettes and terminals for short circuit. Rectify as necessary.
2. Code verification
8 Install air bag simulator in place of passenger-side air bag module.
8 Re-connect DM.
8 Switch on the ignition and wait 30 seconds.
8 Is code 35 still present ?
Yes - Renew DM
8 Examine shorting bar on driver-side air bag connector for correct operation, rectify if necessary.
8 Renew air bag module if shorting bar is operating correctly
NO -
3. on completion
8 Arm and verify the SRS system.
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