For 1990-2009 cars

# SMU - SECTION 6E3 - DRIVEABILITY & EMISSIONS

#### SUBJECT: SERVICE MANUAL UPDATE-SECTION 6E3-DRIVEABILITY AND EMISSIONS REVISED DTC P1406 (PAGE 2 OF 2), EGR PINTLE POSITION ERROR

#### MODELS: 1994-95 BUICK LESABRE, PARK AVENUE, REGAL 1995 BUICK RIVIERA 1994-95 CHEVROLET LUMINA APV 1994-95 OLDSMOBILE EIGHTY EIGHT, NINETY EIGHT, SILHOUETTE 1994-95 PONTIAC BONNEVILLE, TRANS SPORT WITH 3.8L ENGINES (VINS 1, K, L - RPOS L67, L36, L27)

THIS BULLETIN REPLACES THE DTC P1406 EGR PINTLE POSITION ERROR (PAGE 2 OF 2) DIAGNOSTIC CHART IN THE DRIVEABILITY AND EMISSIONS SECTION 6E3-A. A DTC P1406 MAY BE SET DUE TO AN INTERMITTENTLY STICKING EGR PINTLE OR AN OPEN IN THE EGR IGNITION FILTER CIRCUIT. THIS CONDITION MAY BE INTERMITTENT. THE UPDATED CHART INCLUDES STEPS INTENDED TO DIAGNOSE THIS CONDITION.

ALSO, THE FOLLOWING STATEMENTS SHOULD BE ADDED TO THE "DIAGNOSTIC AIDS" SECTION ON THE FACING PAGE.

* STICKING EGR VALVE. AN EGR VALVE WHICH INTERMITTENTLY STICKS PARTIALLY OPEN OR CLOSED CAN CAUSE DTC P1406 TO BE SET, ESPECIALLY WHEN THE ENGINE HAS REACHED NORMAL OPERATING TEMPERATURES AND THE EGR VALVE IS HOT. IT MAY BE POSSIBLE TO ISOLATE THIS CONDITION BY OBSERVING "DESIRED EGR POS." AND "ACTUAL EGR POS." ON THE SCAN TOOL WHILE OPERATING THE VEHICLE. IF A LARGE DIFFERENCE IN THE DESIRED AND ACTUAL POSITIONS IS NOTED, REPLACE THE EGR VALVE.

* INTERNALLY SHORTED EGR VALVE. AN EGR VALVE WHICH IS INTERNALLY SHORTED CAN CAUSE THE 5V REFERENCE CIRCUIT OR THE PINTLE POSITION CIRCUIT TO MEASURE B+ ALL OF THE TIME. MEASURE THE VOLTAGE ON THESE TWO CIRCUITS WITH THE IGNITION "ON". IF THEY MEASURE B+, DISCONNECT THE EGR VALVE AND RECHECK THE VOLTAGE READING. IF THE VOLTAGE GOES BACK TO NORMAL, REPLACE THE EGR VALVE.

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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.

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