INTERMITTENT ENGINCE LOW POWER HESITATION AND/OR STALL. Chevrolet Blazer

SUBJECT: INTERMITTENT ENGINE LOW POWER, HESITATION AND/OR STALL, DTCS P0107, P0122, P1107, P1122, P1406 (REPLACE FUEL TANK PRESSURE SENSOR)

MODELS: 1996 CHEVROLET AND GMC S/T MODELS 1996 OLDSMOBILE BRAVADA WITH 4.3L ENGINE (VINS W, X - RPOS L35, LF6)

CONDITION:

AN OWNER MAY REPORT INTERMITTENT LOW ENGINE POWER, HESITATION AND/OR STALL, AND THE MALFUNCTION INDICATOR LAMP (SERVICE ENGINE SOON LIGHT) ON. ONE OR MORE OF THE FOLLOWING DTC'S MAY BE STORED IN THE VCM. P0107 (MANIFOLD ABSOLUTE PRESSURE SENSOR CIRCUIT LOW VOLTAGE), P0122 (THROTTLE POSITION SENSOR CIRCUIT LOW VOLTAGE), P1107 (MANIFOLD ABSOLUTE PRESSURE SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE), P1122 (THROTTLE POSITION SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE), P1406 (EXHAUST GAS RECIRCULATION VALVE PINTLE POSITION CIRCUIT).

CAUSE:

THERE CAN BE TWO POSSIBLE CAUSES. FIRST, A SHORTED FUEL TANK PRESSURE SENSOR CAN CAUSE THE VCM 5 VOLT REFERENCE VOLTAGE SIGNAL TO BE LOW (BELOW 4 VOLTS). SECOND, A POOR INTERNAL GROUND BETWEEN THE TWO CIRCUIT BOARDS OF THE VCM CAN CAUSE THE VCM TO INCORRECTLY MEASURE THE VOLTAGE AT THE THROTTLE POSITION SENSOR AND THE EGR PINTLE POSITION SENSOR.

CORRECTION:

USE THE FOLLOWING SERVICE PROCEDURE TO DIAGNOSE AND CORRECT THE CONDITION.

SERVICE PROCEDURE:

1. CHECK FOR VCM 5 VOLT REFERENCE SIGNAL AT A CONVENIENT LOCATION SUCH AS A VCM CONNECTOR. IMPORTANT: BOTH VCM REFERENCE LINES ARE INTERNALLY CONNECTED. IF THE 5 VOLT REFERENCE VOLTAGE VALUE IS BELOW 4 VOLTS, THEN CONTINUE WITH STEP 2. IF THE VALUE IS ABOVE 4 VOLTS, PROCEED TO STEP 6. 2. ISOLATE THE FUEL PRESSURE SENSOR AND/OR RELATED WIRING, BY OPENING CONNECTOR C199, A SIX WAY MICRO-PACK CONNECTOR LOCATED IN THE ENGINE COMPARTMENT BY THE LEFT FRONT (DRIVER'S SIDE) INNER WHEEL FENDER AREA, AND RECHECK VCM 5 VOLT REFERENCE VOLTAGE. 3. IF THE VCM 5 VOLT REFERENCE VOLTAGE IS NOW GREATER THAN 4 VOLTS, THE FUEL TANK PRESSURE SENSOR AND/OR RELATED WIRING IS THE LIKELY FAULT. PROCEED TO STEP 4. IF THE 5 VOLT REFERENCE LINE STILL SHOWS LESS THAN 4 VOLTS, THE FUEL TANK PRESSURE SENSOR AND CIRCUIT IS NOT THE CAUSE. PROCEED TO STEP 6. 4. RECONNECT CONNECTOR C199. 5. DISCONNECT THE FUEL PRESSURE SENSOR CONNECTOR AND RECHECK THE VCM 5 VOLT REFERENCE VOLTAGE. IF IT IS ABOVE 4 VOLTS, REMOVE THE FUEL PRESSURE SENSOR AND TEST IT BY CHECKING RESISTANCE AT EACH POSSIBLE COMBINATION OF SENSOR TERMINALS. IF ANY COMBINATION IS LESS THAN 800 OHMS, THE SENSOR SHOULD BE REPLACED. PROCEED TO STEP 7. 6. INSTALL HARNESS JUMPER WIRE, P/N 12167310.

THE FOLLOWING IS A SUMMARY OF THE INSTRUCTIONS INCLUDED WITH THE SERVICE KIT: A. REMOVE THE NEGATIVE TERMINAL FROM THE BATTERY. B. MOVE THE WIRE LOCATED AT CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18 TO CONNECTOR J1 (BLUE), PIN 23. C. INSTALL THE JUMPER WIRE BETWEEN CONNECTOR J2 (RED), PIN 26 AND CONNECTOR J3 (WHITE/GRAY/CLEAR), PIN 18. D. INSTALL THE TAG INCLUDED IN THE KIT AROUND THE VCM WIRING HARNESS. THIS TAG NOTES THAT THE WIRING HARNESS HAS BEEN MODIFIED. E. RECONNECT THE NEGATIVE BATTERY TERMINAL. IMPORTANT: IF THE VEHICLE IS EXPERIENCING ANY TRANSMISSION SHIFTING CONCERNS, REFER TO SERVICE BULLETIN 66-71-04. 7. IF THE CONDITION IS NOT CORRECTED, REFER TO SECTION 3B OF THE SERVICE MANUAL FOR DIAGNOSIS OF EACH STORED DTC STARTING WITH LOWEST CODE. 8. CLEAR ALL STORED DTCS IN THE VCM AND ROAD TEST BEFORE RETURNING THE VEHICLE TO THE OWNER.

THE FOLLOWING TOOLS ARE AVAILABLE FROM KENT-MOORE (1-800- 345-2233) FOR USE IN REMOVING AND RELOCATING THE VCM WIRES: -J41758 TERMINAL TOOL: USED TO REMOVE THE WIRE FROM THE VCM CONNECTOR. -J41759 PUNCH: USED TO PUNCH A NEW HOLE THROUGH THE CONNECTOR SEAL.

PARTS INFORMATION:

P/N DESCRIPTION QTY 16196060 SENSOR - FUEL TANK PRESSURE 1 12167310 HARNESS JUMPER WIRE KIT 1

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME J6327 SENSOR 1.6 HR FUEL TANK PRESSURE REPLACE

N6112 WIRE REPAIR USE PUBLISHED FRONT CHASSIS LABOR OPERATION TIME

FIGURES: 0

CAPTIONS: 0

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.