1994 JAGUAR XJ6 ignition

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

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
0
0
e
0
Issue 1 August 1994 15.1 - 44 X300 EDM

Electrical rl
JOS 1776
1. Instrument Pack 7. Powerwash Relay
2. Body Processor Unit
(BPU) 8. Washer Fluid Level Sensor
3. Oil Pressure Sensor 9. Brake Fluid Level Sensor
4. Coolant Level Sensor 10. Ignition Switch 5. Coolant Temperature Sensor 11. Column Switch
6. Coolant Recirculation Pump Relay 12. Fuel Tank Level Sensor
Fig. 1 Component Location Diagram

Electrical IT
15.2.2 INSTRUMENT PACK CONNECTORS
0
Socket A (24-way)
Pin Circuit Input
1. Fuel used 2. 12V ignition feed 3. Ground 4. Ground 5. Battery feed 6. 12V auxiliary feed 7. Anti-lock fail 8. -
Socket 6 (48-way)
Pin Circuit Input
1. - 2. Speed output 1
3. Speed output 2
4. Trip stalk cycle 5. - 6. - 7- 8. - 9. Generator indicator voltage 10. Brake fluid level 11. - 12. Trip reset 13. Screenwash fluid level 14. Transmission sport mode 15. Seat belt 16. Luggage compartment open
Pin
9.
10.
11.
12.
13.
14.
15.
16.
Pin
17.
18.
19. 20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
Circuit Input
Illumination feed
-
- -
Diagnostic serial output (K) Diagnostic serial input (L)
Distance
-
Circuit Input
Park brake (on)
D.I.
bulb fail - - -
Check engine
Exhaust temperature
Main beam
- - - - - - - -
Fig. 1 Pin Locations
Pin
17.
18.
19.
20.
21.
22.
23.
24.
Pin
33.
34. 35.
36.
37.
38.
39. 40.
41.
42.
43.
44.
45.
46.
47.
48.
Circuit Input
-
Coolant temperature
Fuel level
Oil pressure
Coolant temperature output
Tachometer
input - ECM
-
Circuit Input
Ground - trip keyboard
Traction control status
Trip clear
Coolant level
Side lights (on)
Left D.I. (on)
Right D.I. (on)
Trip
km / miles
General bulb fail
Transmission fail
Air bag fail
Door ajar
- Driver’s
Door ajar - Passenger’s
-
X300 EDM 15.2 - 3 Issue 1 August 1994

E I ect r ical
15.2.3 COMPONENT DESCRIPTION
15.2.3.1 Speedometer
The speed indication input signal, sent as a pulse rate, is generated by an open collectortransistor within the ABS con- trol module. The instrument pack converts the frequency of this signal to drive the speedometer and to provide two
road speed outputs:
Speed output
1 (pin 2,48 way connector)
This output is connected to the radio head unit, security control module and the power steering module.
Speed output 2 (pin
3,48 way connector)
This output is connected to the body processor unit, cruise control control module, air conditioning control module
and the engine management system.
15.2.3.2 Tachometer
The tachometer input, all engine variants, is provided by the engine management control module. When the engine
is running the control module generates three high state pulses per engine revolution.
15.2.3.3
This signal comes direct from the variable resistance type oil pressure sensor, mounted on the engine. The sensor
resistance values range from 75Q (8 Bar) to 330Q (0 Bar).
When the gauge reaches
a pre-determined reading the instrument pack illuminates the warning light.
Engine Oil Pressure and Warning lamp
15.2.3.4 Engine Coolant Temperature
This signal comes direct from the coolant temperature sensor (variable resistance type), mounted on the engine. The
sensor resistance values range from 34Q (hot) to 241Q (cold), when disconnected from the vehicle.
Note: The coolant temperature gauge is calibrated to indicate at approximately 'Normal' for a wide range of normal
engine operating temperatures.
15.2.3.5 Fuel Tank level Gauge and Warning lamp
This signal (pin 20,24-way connector) comes direct from the variable resistor type fuel level sensor. The sensor resis- tance values range from 80 ohms (full tank) to 900 ohms (empty tank).
When the gauge reaches a pre
-determined reading, the instrument pack illuminates the warning lamp.
15.2.3.6
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.
Battery Voltage Gauge and Warning lamp
15.2.3.7 Liquid Crystal Display
A single line, six digit, 7 segment display with six trip function flags used for odometer, trip computer and driver mess- ages.
!Y,Q&: If the instrument pack has not been PECUS programmed, the back illumination of the LCD will not switch on.
Check that a PECUS label is attached to the back of the pack.
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E I ect r ica I
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.
Issue 1 August 1994 15.2 - 6 X300 EDM

15.2.5 SECONDARY WARNING LAMPS - ILLUMINATED AMBER
15.2.5.1 Transmission Fault
The transmission fault indicator is controlled by a signal from the Transmission Control Module (TCM). The signal to
the instrument pack (pin 44,48-way connector) is switched high when a transmission fault occurs, and the indicator
lamp is illuminated.
15.2.5.2 Washer Fluid Level
The washer fluid level sensor, mounted in the fluid reservoir, provides a signal (pin 13, 48-way connector) when the
amount of fluid drops below a predetermined level. The switch is normally in the closed position, providing a low sig-
nal to the instrument pack, when the fluid level is acceptable. If the fluid level drops, the switch will open, removing
the low signal and illuminating the indicator lamp.
15.2.5.3 Bulb Fail
Bulb failure indication is controlled from two different sources:
If a direction indicator lamp fails, a signal is sent to the instrument pack (pin 18,48-way connector) from the Body. :o- cessor Unit (BPU). The signal is normally low but switched high if a bulb failure occurs; thuscausing the bulbfail indica-
If any of the other bulbs, monitored by the three lamp control modules, fail, a signal is sent direct to the instrument
pack (pin 43, 48-way connector). The signal is normally low but switched high if a bulb failure occurs; thus causing
the bulb failure indicator lamp to illuminate.
tor lamp to illuminate.
15.2.5.4 Traction Control Fail
Two traction control lamps are provided: control fail and control off. Both lamps are controlled from one input from
the ABS / TC Control Module.
Under normal operating conditions, the input signal should be high.
If the input line is continuously low, traction con- trol has failed and both lamps will illuminate. If the input signal is a 4 Hz square wave the traction control system is
switched off, therefore the ‘traction off lamp will illuminate.
15.2.5.5 Anti-lock Fail
The input to the instrument pack (pin 7,24-way connector) is provided by the ABS Control Module. The warning lamp
illuminates if the signal voltage is less than 5.0 volts or greater than 11.9 volts.
- 15.2.5.6 Low Fuel Level
This signal (pin 20,24-way connector) comes direct from the variable resistor type fuel level sensor. The sensor resis-
tance values range from 80 ohms (full tank) to 900 ohms (empty tank).
When the gauge reaches
a pre-determined reading, the instrument pack illuminates the warning lamp.
15.2.5.7 Check Engine
The ’checkeng’ indicator will illuminate when the Engine Control Module (ECM) detects a fault within the system, and
sends a signal to the instrument pack (pin 22,48-wayconnector). The signal line is pulled low by the ECM when a fault
is detected.
The indicator lamp will illuminate during each ignition cycle, until the engine fires.
X300 EDM 15.2-7 Issue 1 August 1994

rl E I ect r i ca I
15.2.6 STATUS AND WARNING LAMPS
15.2.6.1 Transmission Sport Mode (green)
The transmission sport mode indicator is controlled by a signal from the Transmission Control Module (TCM). The
indicator is illuminated whenever 'Sport' mode is selected; a low signal is sent to the instrument pack (pin 14,48-way connector).
15.2.6.2 Traction Control OFF (green)
Two traction control lamps are provided: control fail and control off. Both lamps are controlled from one input from
the ABS I TC control module.
Under normal operating conditions, the input signal should be high.
If the input line is continuously low, traction con- trol has failed and both lamps will illuminate. If the input signal is a 4 Hz square wave the traction control system is
switched off, therefore the 'traction
off lamp will illuminate.
15.2.6.3
The operation of the direction indicator 'tell-tales' is controlled by the BPU. The 'tell-tales' are the only indicators on
the instrument pack which can be illuminated with the ignition OFF, for hazard warning.
The signal from the BPU to the instrument pack is pulsed, switching the direction indicators on and
off at the correct
frequency. The 'tell-tales'will illuminate when the signal is low. If the frequency doubles, this signifies that an exterior
direction indicator bulb has failed; the bulb failure warning lamp should also be illuminated.
The signal is fed to two separate inputs to the instrument pack, on the 48
-way connector; pin 40 for LH directional indi- cator 'tell-tale' and pin 41 for RH.
!We: If both direction indicator 'tell-tales' are permanently illuminated; this indicates that the BPU has not been
PECUS programmed. Check that a PECUS label is attached to the BPU.
Direction Indicators - LH & RH (green)
15.2.6.4 Main Beam (blue)
A low signal is supplied to the instrument pack (pin 24,48-way, connector) from the BPU when main beam is selected.
This illuminates the main beam 'tell-tail' indicator lamp.
Issue 1 August 1994 15.2 - 8 X300 EDM