Coolant Alarm and Oil Pressure Alarm Activation (Reprogram PCM)
| Subject: | Coolant Alarm and Oil Pressure Alarm Activation (Reprogram PCM) |
| Models: | 1999 Chevrolet and GMC Medium Duty C6, C7 and B7 Models |
| with 7.4 L Engine (VINs B, D -- RPOs L21, LP4) |
Condition
Some customers may comment that the vehicle's coolant alarm and/or oil pressure alarm activate when the vehicle is stopped and the engine returns to idle. The vehicle will not show any other signs of an overheat or low oil pressure condition while driving.
Cause
The calibration will cause the PCM to activate an alarm when the engine is operating within the normal range.
Correction
Use a scan tool to verify what calibration is programmed into the vehicle's PCM then, reprogram the PCM with the updated calibration listed in this bulletin. This will raise the coolant alarm temperature setting to 112.8°C (235°F) and also adjust the false "Low Oil Pressure" set point to a more accurate specification at engine idle.
Calibration Information
Option | Old Part Number | New Part Number |
|---|---|---|
L21 and LVA and MWX | 9377551 | 9384501 |
L21 and LVA and MWE | 9377561 | 9384511 |
L21 and KYR and MWX | 9377571 | 9384521 |
L21 and KYR and MWE | 9377581 | 9384531 |
L21 and MWX-KRY/LVA | 9377591 | 9384541 |
L21 and MWE-KYR/LVA | 9377601 | 9384551 |
LP4 and MWX and NM8 | 9377611 | 9384561 |
LP4 and LVA and MWX | 9377621 | 9384571 |
LP4 and KYR and MWX | 9377631 | 9384581 |
LP4 and MWX-KRY/LVA/NM8 (B 700) LP4 and MWX-NM8 | 9377641 | 9384591 |
LP4 and LVA and MWE | 9377651 | 9384601 |
LP4 and KYR and MWE | 9377661 | 9384611 |
LP4 and MWE-KYR/LVA (B 700) LP4 and MW | 9377671 | 9384621 |
The calibrations listed are electronic calibrations and are NOT available from GMSPO. Calibrations will be available from Techline starting June 1999, on the 1999 Disk 12 CD ROM.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation | Description | Labor Time |
|---|---|---|
J6355 | PROM - Reprogramming on Vehicle | Use Published Labor Operation Time |
