SMU - SEC. 6E3-REV. DTC P1531 & C-10A CHARTS AND CIRCUIT

SUBJECT: SERVICE MANUAL UPDATE-SECTION 6E3-REVISED DTC P1531 AND C-10A (1 OF 3) CHARTS AND CIRCUIT DESCRIPTIONS

MODELS: 1994 CHEVROLET LUMINA APV 1994 PONTIAC TRANS SPORT 1994 OLDSMOBILE SILHOUETTE WITH 3800 ENGINE (VIN L - RPO L27)

THIS BULLETIN UPDATES THE FOLLOWING PAGES IN THE SERVICE MANUAL:

*DTC P1531 (LOW A/C REFRIGERANT CHARGE) CHART AND FACING PAGE CIRCUIT DESCRIPTION FOUND ON PAGES 6E3-A-88/89 (BOOK 2).

*C-10A (1 OF 3) A/C CLUTCH CIRCUIT DIAGNOSIS CHART AND FACING PAGE CIRCUIT DESCRIPTION FOUND ON PAGES 6E3-C10-2/3 (BOOK 2).

THE CIRCUIT DESCRIPTIONS FOR THE C-10A AND DTC P1531 CHARTS SHOULD HAVE THE FOLLOWING THREE PARAGRAPHS ADDED:

THE PCM MONITORS THE A/C REQUEST LINE (CKT 762) FOR A SWITCHING VOLTAGE CONTROLLED BY THE PRESSURE CYCLING AND HIGH PRESSURE CUTOFF SWITCHES. IF VOLTAGE IS PRESENT AT THE PCM FOR LESS THAN 1.5 SECONDS, 10 OR MORE TIMES CONSECUTIVELY WITHIN 15 MINUTES (HIGHER THAN NORMAL CYCLING), DTC P1531 WILL SET AND THE PCM WILL NOT PROVIDE A GROUND FOR THE A/C RELAY (CKT 459) FOR THE REST OF THE IGNITION CYCLE.

IF CODE P1531 IS SET 3 CONSECUTIVE IGNITION CYCLES, THE PCM WILL NOT TURN THE A/C RELAY ON UNTIL DTC P1531 IS CLEARED. A DTC P1531 WILL NOT ILLUMINATE THE MIL (SERVICE ENGINE SOON) LAMP AND CAN ONLY BE CLEARED WITH A SCAN TOOL OR BY DISCONNECTING THE POWER SUPPLY TO THE PCM.

AFTER A DTC P1531 HAS BEEN CLEARED FROM THE PCM, IF THE FAULT IS STILL PRESENT, IT MAY NOT RESET IF THE VEHICLE IS RUN AT IDLE. A/C REFRIGERANT PRESSURE MUST INCREASE ENOUGH TO CAUSE THE COMPRESSOR TO CYCLE RAPIDLY, THIS WILL REQUIRE ENGINE SPEEDS OF 2000 RPM.

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