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Jaguar XJ-S 1990 – 1988 90 ENGINE PERFORMANCE Self Diagnostics

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Jaguar XJ-S 1990 - 1988-90 ENGINE PERFORMANCE Self-Diagnostics


Jaguar XJ-S 1990 - INTRODUCTION

NOTE: The XJS 5.3L V12 does not have a check engine light or diagnostic capabilities.

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES in BASIC TESTING article, proceed with self-diagnostics. If no fault codes are present after entering self-diagnostics, proceed to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).


Jaguar XJ-S 1990 - SELF-DIAGNOSTIC SYSTEM CHECK ENGINE LIGHT CHECK ENGINE Light


Vehicles are equipped with a malfunction indicator (CHECK ENGINE) light. When the CHECK ENGINE light remains on, the self-diagnostic system has detected a system failure.


Jaguar XJ-S 1990 - Hard Failures


Hard failures cause CHECK ENGINE light to glow. Fault codes are stored in Electronic Control Module (ECM) memory. All codes except Codes 26 and 44 will cause CHECK ENGINE light to remain illuminated (with ignition on) until fault is corrected and ECM memory is cleared.

Codes 26 and 44 and the CHECK ENGINE light will remain on only until next ignition on/off cycle. Code will no longer be available to driver, but will still be stored in ECM memory.

If light comes on and remains on during vehicle operation, cause of malfunction must be determined using TROUBLE CODE IDENTIFICATION table. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional but poor driveability may occur.


Jaguar XJ-S 1990 - RETRIEVING CODES


When a system fault has been detected, trouble codes can be retrieved. Vehicle must be stationary. With ignition switch in OFF position, wait 5 seconds and then turn ignition switch to position II. DO NOT start engine. Press Vehicle Condition Monitor (VCM) button, located on VCM/trip computer display panel.

Applicable trouble code will be displayed on display panel. See appropriate code in TROUBLE CODE IDENTIFICATION table for probable cause. When engine is started, trouble code will be deleted from written display, but the CHECK ENGINE light will remain on.


Jaguar XJ-S 1990 - TROUBLE CODE DEFINITION (DTC) IDENTIFICATION


NOTE: For XJ6 models, additional codes not listed in this article have been updated as per TSB SECTION 18, No. 3 - Faulty Fuel Systems: New Feedback Fault Codes.


Jaguar XJ-S 1990 TROUBLE CODE IDENTIFICATION

No. System Affected Probable Cause
12 Mass Airflow (MAF) Sensor Not In Operating Range
14 Coolant Temp. Sensor Not In Operating Range
16 Air Temperature Sensor Not In Operating Range
17 Throttle Position Sensor Not In Operating Range
18 Throttle Potentiometer/MAF Sensor Resistance Low at WOT
19 Throttle Potentiometer/MAF Sensor Resistance High At Idle
22 Heated O2 Sensor/Fuel Pump Relay Open Or Short Ckt @ Idle
23 Fuel Control Rich Exhaust Indicated
24 Ignition Amplifier Open Or Short Circuit
26 Air Leak/Running Lean Lean Exhaust/Vacuum Leak
29 Electronic Control Module Self Check
33 Fuel Injector Circuit Open Or Short Circuit
34 Fuel Injector Circuit Faulty Injector
37 EGR Solenoid Valve Short Or Open Circuit
39 EGR Function Faulty System Operation
44 Heated Oxygen Sensor Rich Or Lean Condition
46 Idle Air Control Valve (Coil 1) Open Or Short Circuit
47 Idle Air Control Valve (Coil 2) Open Or Short Circuit
48 Idle Air Control Valve Position Not Within Specification
66 Air Injection Pump Relay Short Circuit Or Faulty Pump
68 Vehicle Speed Sensor Incorrect Signal Voltage
69 Park/Neutral Position Switch Ckt Engine Cranks In Drive
89 EVAP Canister Purge Control Valve Voltage Out Of Range


Jaguar XJ-S 1990 - DIAGNOSTIC TROUBLE CODE FAULT DIAGNOSIS DTC 12: Mass Airflow Sensor


  1. Ensure engine is not misfiring. If necessary, check crankshaft position sensor, timing ring, and sensor air gap. Check voltage at mass airflow sensor pin No. 1 or 2 (zero volts) and pin No. 5 (12 volts).
  2. Check mass airflow sensor output voltage. For specifications, see appropriate article in this section:

Ensure mass airflow sensor has not been subjected to water. If necessary, dry out air intake system. Check intake duct for blockage. Repair or replace as necessary.


Jaguar XJ-S 1990 - DTC 14: Engine Coolant Temperature Sensor


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 16: Air Temperature Sensor


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 17: Throttle Position Sensor


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 18: Throttle Position Sensor


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 19: Throttle Position Sensor/Mass Airflow Sensor Calibration


Ensure Idle Air Control Valve (IACV) and overrun fuel cutoff operate with the throttle closed. Check throttle position sensor. Check voltage at mass airflow sensor pin No. 1 or 2 (zero volts) and pin No. 5 (12 volts). Check mass airflow sensor output voltage. For adjustment procedures, see appropriate article in this section. Repair or replace as necessary.


Jaguar XJ-S 1990 - DTC 22: Heated Oxygen Sensor/Fuel Pump Relay


  1. Ensure pin 85 at fuel pump/oxygen sensor heater relay is grounded while engine is cranking. If not grounded, go to next step. If grounded, go to step 3).
  2. Check that Engine Control Module (ECM) terminal No. 7 (Pink/Brown wire) is grounded while engine is cranking. If not grounded, replace ECM. If grounded, check for open wiring harness between ECM and fuel pump/oxygen sensor heater relay.
  3. With ignition on, check for 12 volts at pin No. 86 of fuel pump/oxygen sensor heater relay. If voltage is not present, check for an open circuit in White/Brown wire back to main relay. If voltage is present, check or replace faulty fuel pump/oxygen sensor heater relay.

Jaguar XJ-S 1990 - DTC 23: Fuel Control, Running Rich


  1. If EVAP canister purge control valve has an electrical signal, go to DTC 89. If no electrical signal is present, check fuel pressure at idle. Fuel pressure should be 36.3 psi (2.5 kg/cm2 ) with vacuum hose connected to fuel pressure regulator, or 43.5 (3.0 kg/cm2 ) with vacuum hose disconnected.
  2. If fuel pressure is incorrect, check fuel pressure return line for blockage. Check vacuum signal if fuel pressure is high with vacuum hose connected. If necessary, replace fuel pressure regulator.
  3. If fuel pressure is okay, check for leaking fuel injector and DTC 34. Check mass airflow sensor. Repair or replace as necessary.

Jaguar XJ-S 1990 - DTC 24: Ignition Amplifier


Check continuity of ignition amplifier wiring harness. Check for faulty ignition amplifier. Repair or replace as necessary.


Jaguar XJ-S 1990 - DTC 26: Air Leak, Running Lean


  1. Check if air pump is running when engine is hot. Air pump should work for a short period after each hot start or work for several minutes following a cold start. If air injection system is not functioning properly, check air injection system.
  2. If air injection system is functioning properly, check exhaust manifold or oxygen sensor for leakage. Check that fuel pressure is correct when engine is running under load. Repair or replace as necessary.
  3. Check for vacuum leaks to A/C system and EGR valve. Check for leaks at EGR valve transfer pipe and intake manifold. Check air induction system for leaks at elbow and hoses. Check PCV and EVAP systems for leaks, including dipstick. Repair or replace as necessary.

Jaguar XJ-S 1990 - DTC 29: Electronic Control Module


Replace faulty Electronic Control Module (ECM).


Jaguar XJ-S 1990 - DTC 33: Leaking Fuel Injector


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 34: Leaking Fuel Injector


Information is not available from manufacturer.


Jaguar XJ-S 1990 - DTC 37: EGR Solenoid Valve


  1. Ensure EGR control solenoid is properly connected. Check continuity of wiring harness between ECM and EGR control solenoid. Repair or replace as necessary.
  2. Ensure EGR control solenoid resistance is approximately 40 ohms. Apply parking brake and service brakes. Ensure ECM is grounding EGR control solenoid Green/Red wire with engine at 1200 RPM (engine at normal operating temperature). Replace ECM if it is not grounding EGR control solenoid.

Jaguar XJ-S 1990 - DTC 39: EGR Function


  1. With engine at normal operating temperature and transmission in Neutral, lift EGR valve diaphragm. Engine should run rough and RPM should decrease. If engine does not run rough, check EGR transfer pipe, intake manifold, and EGR valve for blockage.
  2. If engine runs rough, apply parking brake and service brakes. With engine hot, ensure vacuum signal to EGR valve is present at 1200 RPM. If vacuum signal is not present, ensure ECM is grounding EGR control solenoid Green/Red wire or check vacuum hose routing.
  3. If vacuum signal is present, ensure EGR valve functions properly when vacuum is applied. Replace EGR valve if necessary. Ensure ECM is receiving EGR temperature sensor signal. See appropriate article:

Check continuity of wiring harness between ECM and EGR temperature sensor. Repair or replace as necessary.


Jaguar XJ-S 1990 - DTC 44: Heated Oxygen Sensor


  1. Ensure heated oxygen sensor is properly connected. Check continuity of wiring harness between ECM, fuel pump/oxygen sensor heater relay, and heated oxygen sensor.
  2. Ensure heated oxygen sensor is receiving 12 volts from fuel pump/oxygen sensor heater relay. Check heated oxygen sensor ground circuit. Ensure tip of heated oxygen sensor is not damaged. Repair or replace as necessary.

Jaguar XJ-S 1990 - DTC 46 & 47: Idle Air Control Valve


Check ECM main relay power input, ignition switch power input, and ECM battery power input circuits to ECM small signal ground circuit. See appropriate article:

Voltage input readings should be within 200 millivolts of each other. If necessary, repair wiring harness. Check for faulty ECM.


Jaguar XJ-S 1990 - DTC 48: Idle Air Control Valve Position


Ensure idle air control valve hoses are not blocked, pinched, or restricted. Ensure idle air control valve is not stuck. Repair or replace as necessary. Reset base idle speed. See appropriate article:


Jaguar XJ-S 1990 - DTC 66: Air Injection Pump Relay


  1. If air injection pump is operating continuously, air injection pump relay output circuit (Green/Black wire) may be grounded. Check wiring harness for short circuit to ground. If necessary, repair wiring harness or replace faulty air injection pump relay.
  2. If air injection pump does not operate continuously, ensure air pump works for a short period after each hot start or works for several minutes following a cold start. Check air injection pump relay output circuit at pump relay. See appropriate article:

If necessary, repair wiring harness or replace faulty air injection pump relay. Check for faulty ECM.


Jaguar XJ-S 1990 - DTC 68: Speed Sensor


Road test vehicle and check if instrument cluster indicates road speed. If road speed is not indicated, repair or replace speed sensor/instrument cluster. If road speed is indicated, check wiring harness between ECM and instrument cluster. If necessary, repair wiring harness. Check for faulty ECM.


Jaguar XJ-S 1990 - DTC 69: Park/Neutral Position Switch


  1. Check for input signal to ECM on terminal No. 3 (Yellow wire) with transmission in Park or Neutral. If signal is present, reset gear selector switches and/or check decoder module.
  2. If signal is not present, check idle fuel demand (PNPS) input circuit at ECM. See appropriate article:

If necessary, repair wiring harness. Check for faulty ECM.


Jaguar XJ-S 1990 - DTC 89: EVAP Canister Purge Control Valve


Check wiring harness and connectors for intermittent fault. Check EVAP canister purge control valve function. Valve is functional if "click" can be heard or if touch can detect it is functioning properly. Check for faulty ECM.


Jaguar XJ-S 1990 - CLEARING CODES


Turn ignition switch to OFF position. Remove negative battery cable for at least 30 seconds to clear ECM trouble code memory.


Jaguar XJ-S 1990 - ECM LOCATION


ECM is located under dash on passenger side of vehicle, behind lower dash panel.


Jaguar XJ-S 1990 - SUMMARY


If no hard fault codes are present, see TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.