Engine Controls - Driveability/Starting Issues/DTC's/MIL
MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY# 76-65-04 - (Mar 3, 1997)
SUBJECT:
MALFUNCTION INDICATOR LIGHT (MIL) ON, POOR DRIVEABILITY CONDITIONS (PERFORM FLASH CALIBRATION)
MODELS:
1996-97 CHEVROLET AND GMC LIGHT DUTY TRUCKS
1996-97 CHEVROLET TILTMASTER AND GMC FORWARD W4 MODELS
1996-97 OLDSMOBILE BRAVADA
WITH 4.3L, 5.0L, 5.7L ENGINES (VINS X, W, M, R - RPOS LF6, L35, L30, L31)
CONDITION:
AN OWNER MAY REPORT THAT THE MALFUNCTION INDICATOR LIGHT (MW) IS ON AND/OR THE VEHICLE HAS ONE OR MORE OF THE FOLLOWING DRIVEABILITY CONDITIONS.
1. 5.7L (L31) ONLY: SURGE OR CHUGGLE AT SPEEDS OF 42 TO 65 MPH WHILE AT STEADY SPEED OR UNDER LIGHT TO MODERATE ACCELERATION WITH THE TCC APPLIED.
2. MIL ON WITH DTC P0172 OR P0175 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS.
3. MIL ON WITH DTC P1406 STORED AND ROUGH ENGINE OR POOR DRIVEABILITY SYMPTOMS.
4. WHEN OPERATING AT ALTITUDES ABOVE 5,000 FEET, AN AUDIBLE SPARK KNOCK NOISE IS HEARD.
5. HESITATION AND/OR MISFIRE DURING LIGHT CRUISE CONDITIONS DUE TO IGNITION CROSS-FIRE WITH NO DTC STORED. THIS WILL ONLY OCCUR ON V-6 ENGINES WITH CAM RETARD OFFSET IN EXCESS OF 26 DEGREES AND V-8'S WITH CAM RETARD OFFSET IN EXCESS OF 15 DEGREES.
6. THE MIL MAY BE ON AND A DTC STORED FOR AN ENGINE MISFIRE BUT NO MISFIRE OCCURRED.
7. ENGINE EXHIBITS AN IDLE SPEED SURGE OR ROLL.
1996 MODELS ONLY
8. MIL ON WITH DTC P0102 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS.
9. 5.0L (L30) + 5.7L (L31) ONLY: DIFFICULT STARTING IN EXTREME COLD (BELOW 0 DEGREES F) CONDITIONS.
10. 5.7L (L31) ONLY: POORER THAN EXPECTED FUEL ECONOMY WHEN HEAVILY LOADED.
1997 MODELS ONLY
11. MIL ON WITH DTC P0121 STORED BUT NO REPORTED DRIVEABILITY SYMPTOMS.
12. C/K + S/T MODELS WITH EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN EXHAUST BACKFIRE MAY OCCUR WHILE SHIFTING WITH MODERATE THROTTLE AT ENGINE SPEEDS ABOVE 3500 RPM.
13. EITHER V-6 ENGINE AND MANUAL TRANSMISSION: AN ENGINE FLARE BETWEEN SHIFTS MAY BE NOTED WHEN THE ENGINE IS COLD.
14. C/K, S/T AND MIL MODELS EQUIPPED WITH L35 V-6 ENGINE, AN IMPROVEMENT TO THE VAPOR CANISTER PURGE DIAGNOSTICS IS INCORPORATED INTO THE NEW CALIBRATIONS SO THAT THE TECH II CAN TURN ON CANISTER PURGE AT IDLE SPEED.
CORRECTION:
FOLLOW THE STRATEGY BASED DIAGNOSTIC STEPS FOR THE CUSTOMER'S REPORTED SYMPTOMS. IF DIAGNOSIS DOES NOT REVEAL A CAUSE, REFER TO THE TABLES BELOW FOR THE APPLICABLE CALIBRATION CHANGE. PERFORM PROGRAMMING PER THE LATEST TECHLINE INFORMATION FOR PROGRAMMING PROCEDURES.
IMPORTANT:
THE CALIBRATIONS LISTED ARE FLASH CALIBRATIONS AND ARE NOT AVAILABLE FROM GMSPO. THEY ARE AVAILABLE ON 1997 TECHLINE CD DISC 5 AND LATER.
WARRANTY INFORMATION:
FOR VEHICLES REPAIRED UNDER WARRANTY, USE THE TABLE.
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