C 3500 Truck 2WD V8-8.1L VIN G (2001)
Engine Control Module: Customer Interest
PCM - Service Engine Lamp ON/DTC P1781 Set
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 01-06-04-020
Date: March, 2001
TECHNICAL
Subject:
Service Engine Soon Indicator Lamp On, DTC P1781 Set
(Reprogram Engine Control Module)
Models:
2001
Chevrolet and GMC C/K 2500/3500 Series Pickup Models With 8.1L (RPO L18) Gas Engine and Allison Automatic Transmission (RPO M74)
Condition
Some customers may comment that the Service Engine Soon indicator lamp is illuminated. Technicians may find DTC P1781 (Transmission Control
Module - Incorrect Voltage Level on MIL Request Circuit) stored in the ECM.
Correction
If the P1781 diagnostic chart found in SI2000 does not lead to a correction, update the calibration within the ECM using normal SPS reprogramming
procedures.
Important:
After reprogramming, the technician must use the Tech 2 to clear diagnostic trouble codes in the ECM because the process of reprogramming the
module will result in P1781 being logged again.
The calibrations are electronic calibrations and are NOT available from GMSPO. Calibrations are available from Techline starting January, 2001 on the
TIS 2000 version TIS 02/2001 data.
Warranty Information
For vehicles repaired under warranty, use table shown.
DISCLAIMER
