HARSH CHUGGLE/MISS/HESITATION DTC PO71 (CHECK/REPAIR DTC). Cadillac DeVille 1994

SUBJECT: HARSH CHUGGLE, SURGE, MISS, HESITATION ACCOMPANIED BY A HISTORY DIAGNOSTIC TROUBLE CODE PO71 (CHECK/REPAIR PER DTC)

MODELS: 1993 CADILLAC ALLANTE, ELDORADO COUPE AND SEVILLE SEDAN 1994 CADILLAC ELDORADO, SEVILLE AND CONCOURS WITH 4.6L ENGINE (VINS Y AND 9 - RPOS LD8 AND L37)

CONDITION:

SOME OWNERS MAY EXPERIENCE ENGINE ROUGHNESS, HARSH CHUGGLE DURING HIGHWAY DRIVING, SURGE, MISS AND HESITATION WITH NO MIL OR MESSAGE AND A HISTORY DIAGNOSTIC TROUBLE CODE PO71.

CAUSE:

CODE PO71 SETS WHEN THERE IS A RAPID CHANGE IN MAP WITH NO CORRESPONDING CHANGE IN THE TP SENSOR OR RPM. A DTC PO71 MAY BE A SYMPTOM OF A DRIVEABILITY CONDITION SUCH AS BACKFIRE, STALL, OR LOSS OF POWER. A FALSELY SET DTC PO71 MAY BE CAUSED BY INTERNAL "NOISE" IN SOME NORTHSTAR PCMS INDUCED INTO THE INTERNAL PCM MAP CIRCUIT.

NOTE: ENGINE OIL NEAR OR ON MAP SENSOR IS A NORMAL CONDITION. MAP SENSORS SHOULD NOT BE REPLACED IF ENGINE OIL IS PRESENT.

CORRECTION:

THE NORTHSTAR'S PCM HAS BEEN REDESIGNED TO CORRECT THIS INTERNAL CIRCUIT "NOISE" CONDITION. TO DIAGNOSE AND REPAIR THE ABOVE CONDITIONS, PERFORM THE FOLLOWING PROCEDURES:

1. IF THE VEHICLE HAS MULTIPLE DIAGNOSTIC TROUBLE CODES AND DTC PO71, DIAGNOSE AND REPAIR THE **OTHER** DIAGNOSTIC TROUBLE CODES FIRST.

2. IF THERE WAS A BACKFIRE OR STALL, DIAGNOSE THAT CONDITION AS OUTLINED IN SECTION 6E-B OF THE SERVICE MANUAL.

3. IF THE VEHICLE IS A 1993 AND HAD A LOSS OF POWER AFTER AN EXTENDED HIGHWAY DRIVE, PERFORM THE PROCEDURES OUTLINED IN CORPORATE BULLETIN 216306 (GM OF CANADA 93-6-118; CADILLAC T-93-49 IN GROUP 6E).

4. IF THE VEHICLE IS A 1993, PERFORM THE PROCEDURES OUTLINED IN CORPORATE BULLETIN 316005 (GM OF CANADA 93-6-118; CADILLAC T-93-101 IN GROUP 6E).

5. IF THE VEHICLE HAS A HARSH CHUGGLE DURING HIGHWAY DRIVING, SURGE, MISS OR HESITATION ACCOMPANIED BY A HISTORY DTC PO71, INSPECT THE SERVICE PART NUMBER ON THE PCM. IF IT IS ONE OF THE PRESENT SERVICE PART NUMBERS LISTED BELOW, REPLACE THE PCM USING ONE OF THE APPROPRIATE **NEW** SERVICE PART NUMBERS LISTED BELOW.

6. IF THE PCM HAS THE NEW SERVICE PART NUMBER, FOLLOW THE APPROPRIATE SERVICE INFORMATION MANUAL PROCEDURES FOR DTC PO71 AND INSPECT THE MAP SENSOR CONNECTIONS AND CIRCUITRY.

PARTS INFORMATION:

PRESENT NEW DTC PO71 DESCRIPTION APPLICATIONS SERVICE P/N SERVICE P/N ----------- ------------ ----------- ------------- POWERTRAIN CONTROL MODULE 1993 V WITHOUT V4J 16159277 16207768 POWERTRAIN CONTROL MODULE 1993 V,E,K WITH V4J 16180517 16197429 POWERTRAIN CONTROL MODULE 1994 E/K + KSP 16196402 16197429

PARTS ARE EXPECTED TO BE AVAILABLE ON MAY 23, 1994.

FIGURES: 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.