Explorer 4WD V6-245 4.0L (1991)
Fuel Pressure: Customer Interest
MIL Intermittently ON/Error Codes 41 or 42 Set
Article No.
92-6-15
March 11, 1992
WARNING LIGHT - CHECK ENGINE - INTERMITTENTLY LIT WITH NO DRIVE SYMPTOMS EVIDENT - VEHICLES WITH 4.0L ENGINE
AND AUTOMATIC TRANSMISSION
LIGHT TRUCK:
1991 EXPLORER
CALIBRATION: 0-58A-R00, 0-58B-R00
WARNING: THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER
ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR
LOCAL LAWS.
This TSB article is being republished in its entirety to delete the reference to 1992 vehicles and to change the condition code.
ISSUE:
The "Check Engine" Light may come on intermittently when generally there is no other drive symptom evident and a Self-Test error code
"41" is stored in memory. Key On Engine Running Self-Test (KOER) error codes "41 or 42" may also be present. Since several engine
concerns can set the "Check Engine" light and produce Self-Test error codes, it is important to carefully follow the diagnostics listed below
and in the 1991 Engine/Emissions Diagnosis Manual to avoid replacing good parts.
ACTION:
If service is required, use the following service procedure to help identify and correct intermittent "Check Engine" Light complaints.
1.
Perform KOEO and KOER Self-Test as soon as possible after the customer notices that the "Check Engine" Light is on and record all codes.
^
If a code "41" in KOEO (continuous memory) test and/or code "41 or 42" in KOER Test are the only codes found, proceed with Step 2.
^
If other codes are present refer to the 1991 Powertrain Control/Emissions Diagnosis Manual for direction.
2.
Inspect for air leaks between the mass air flow sensor and the upper intake manifold. Check the air hose itself as well as the connections (leaks
allow unmetered air to lean out the fuel mixture). Repair as required.
3.
Inspect the PCV valve, the vacuum tree, and all the vacuum lines and connections for vacuum leaks. Repair as required.
4.
Confirm that the fuel pressure is between 30 and 40 PSI with the engine running.
a.
Check to see that the fuel pressure does not bleed off more than 10 PSI in one (1) minute after engine shutdown.
b.
If this test fails, refer to the Powertrain Control/Emissions Diagnosis Manual, Fuel Delivery Systems Section, for system diagnosis.
5.
Clear all codes and rerun the KOEO and KOER Self-Tests.
a.
If repairs were made and NO error codes are present, service is complete.
b.
If NO repairs were made, and there are NO error codes present, go to Step 8.
c.
If error code "41 or 42" is found in KOER Self-Test, proceed with Steps 6 or 7.
6.
Perform the following tests for code "41" KOER.
a.
Perform the wiggle test to look for intermittent harness concerns.
b.
Disconnect the HEGO sensor and the EEC module.
c.
Check the harness for continuity and for possible short circuits to ground.
7.
Perform the following tests for code "42" KOER.
a.
Check the fuel pressure (Step 4 above) and repair any concerns found.
b.
Disconnect the HEGO and check the HEGO heater voltage with the key ON. The absence of power to the HEGO heater will prevent the