Wagoneer L6-242 4.0L VIN M FI (1988)
Oxygen Sensor Heater Relay: All Technical Service Bulletins
O2 Sensor Heater Relay - Fault C1003 Set
Models
1988 Cherokee, Wagoneer And Comanche With 4.0L Engine
Subject
MS 1700 Diagnostic Tester Fault C1003
-
O2 Heater Line High
Index
ELECTRICAL
Date August 1, 1988
No.
08-54-88
P-3083
(C08-59)
SYMPTOM/CONDITION
The MS 1700 Diagnostic Tester may display a "Fault C1003 - O2 Heater Line High" while performing a "Vehicle Test" on some early built 1988
Cherokee, Wagoneer and Comanche vehicles with a 4.0L engine. This Fault could be caused by an oxygen sensor (O2) heater relay connector which is
improperly wired for use with the 1988 MS 1700 Diagnostic Tester Cartridge (PN 8980-003- 021).
DIAGNOSIS
If a "Fault C1003 - O2 Heater Line High" occurs, verify that the vehicle being tested is a 1988 Cherokee, Wagoneer or Comanche with a 4.0L engine
and the MS 1700 Diagnostic Tester Cartridge is PN 8980-003-021. Turn the ignition switch to the "ON" position. Check for voltage at the diagnostic
connector pin D2-9. If the initial voltage is greater than 9 volts and drops to 0 volts after 3-5 seconds, the O2 heater relay connector is properly wired
and the technician should refer to the C1003 fault tree in the MS 1700 Diagnostic Tester Manual for diagnostic procedures. If the voltage is greater than
9 volts and does not drop to 0 volts after 3-5 seconds, the O2 heater relay connector wiring is not compatible with the 1988 Diagnostic Tester Cartridge
and the technician should perform the following repair procedures.
REPAIR PROCEDURES
1.
Turn the ignition switch to the OFF position.
2.
Disconnect the battery negative cable from the battery and remove the relay cover.
3.
Remove the four relay connectors from the bracket on the right inner fender panel by squeezing the locking tabs on the fender side of the bracket.
