VCM - Feedback Fueling Fault Code Changes
88jaguar02FUELING FAILURE CODES
SECTION: 18
No: 3
Model: XJ6 3.6 Date, JUNE, 1988
KEY POINTS: VCM FAULT CODES
Beginning with VIN 521255, XJ6 3.6 vehicles incorporate high compression engines. These vehicles are equipped with either a DBC 3713 or DBC 4413 Engine Management Control Unit.
To provide a more detailed description of a feedback fueling fault (displayed on the VCM), three of the eight fuel failure codes have been changed. Previously, all feedback fueling faults were displayed as a single fuel failure code, code number 4.
The VCM fault code identification is as follows:
CODE DESCRIPTION
*1 Lambda sensor open circuit.
2 Air mass meter failure (open circuit/short circuit to
ground).
3 Coolant temperature sensor failure.
*4 Feedback fueling full rich.
5 Air mass meter failure (low throttle potentiometer
voltage with high air mass meter voltage).
6 Air mass meter failure (high throttle potentiometer
voltage with low air mass meter voltage).
*7 Feedback fueling full lean.
8 Intake manifold air temperature sensor failure (open
circuit/short circuit to around).
* = Revised Codes
Code numbers 4 and 7, "Feedback fueling" refers to the extent that the lambda sensor would have in altering the fuel mixture.
Example: If a large intake manifold air leak existed, the lambda would sense an abnormally lean exhaust gas. The ECU, acting on the lambda sensor's input, would enrichen the fuel mixture to compensate. Because the lambda's control is relatively small, the feedback fueling would be full rich and the failure code number 4 would be displayed.
Low compression engine vehicles incorporating ECU (DBC 2911, or 3711) will retain the original fueling failure codes. Additional fuel failure code information can be found on page 29 of the XJ6 3.6 Technical Introduction Book, (S 20).
CAUTION: Part numbers included in Service Bulletins are for reference only and should always be cross referenced with the latest parts information.