Date of issue 11/02 Bulletin Number 303-58 Page 1 of 6
11/02V8 XJ Series/XK
1999-2001 MY XK Range
1999-2001 MY V8 XJ Series
Check Engine MIL - DTC P0121 Flagged –
Connector Material Mismatch –
AJ27 Engines – Modify Harness
On some 1999-2001 XK and XJ vehicles within the above VIN ranges, with AJ-27 engines,
Diagnostic Trouble Code (DTC) P0121 (Throttle Position Signal) may be present. A possible
cause is a mismatch of electrical connector terminal materials between the Throttle Position
Sensor (TPS) and the wiring harness electrical connector (gold terminals on the TPS and tin
terminals on the wiring harness).
For 1999 MY vehicles, also refer to Technical Bulletin 303-S498, Service Action S498.
On a customer complaint basis only, install new gold terminals into the TPS wiring harness
electrical connector as follows:
HARNESS MODIFICATION PROCEDURE
1. Record customer preferences as described in Technical Bulletin 414-01. Remove battery
cover and disconnect battery.
2. Open hood and fit fender protectors.
3. On XK Series vehicles:
• Remove induction elbow to throttle housing securing screws.
• Disconnect induction elbow from throttle housing and reposition for access.
On V8 XJ Series vehicles:
• Remove left and right hand bulkhead covers.
• Remove engine compartment rear cover.
• Remove nut securing engine harness main electrical connector to support bracket.
• Reposition main electrical connector upwards.
4. On all vehicles, disconnect TPS electrical connector (Illustration 1).
TPS ELECTRICAL CONNECTOR