Engine - Intermittent Miss, Surge, or Lack of Power

Group Ref.: 6E - Engine Fuel & Emission

Bulletin No.: 476513

Date: June, 1994

SUBJECT:
INTERMITTENT MISS, SURGE, OR LACK OF POWER WHILE DRIVING USUALLY ON ACCELERATION (REPAIR WIRING/REPOSITION HARNESS)

MODELS:
1993-94 CADILLAC ELDORADO, SEVILLE, AND CONCOURS WITH 4.6L NORTHSTAR ENGINE (VINS Y, 9 - RPOs LD8, L37)

THIS BULLETIN CANCELS AND SUPERSEDES BULLETIN NUMBER 476401 TO CORRECT THE CATEGORY IDENTIFIER/GROUP REFERENCE. PLEASE DISCARD BULLETIN 476401 (GROUP REFERENCE 6 - ENGINE).

CONDITION:

Some owners may experience an intermittent miss, surge or lack of power on a moderate to hard acceleration or at steady speeds with no PCM DTC codes set.

CAUSE:





This condition may be caused by an intermittent short to ground on the Park/Neutral input (PI79) to the PCM. The Park/Neutral input (PI79), is a normally "HI" input to the PCM when the gear selector is in any of the Drive positions and "LO" in Park or Neutral. If (PI79) goes "LO" while driving, the PCM will enable the Torque Management mode. During the Torque Management mode, the PCM will reduce engine power by retarding the timing and shutting off 4 injectors. The Park/Neutral input, circuit 434 (an orange/black wire), may be shorting to the transaxle case near the PRNDL switch connector (see Figure 1).

CORRECTION:
To repair this condition, use the wiring repair procedures in the Service Manual, Section 8A-5. After the circuit has been repaired, the harness should be repositioned using plastic tie straps to prevent contact with the transaxle case caused by engine movement during acceleration.

WARRANTY INFORMATION:
For vehicles repaired under warranty, use:

Labor Operation Labor Time

J6383 Use Published Labor
Time