Subject: | Fuel and Temperature Gauge Inoperative, Low Fuel and Battery Light On, PRNDL Inoperative |
Models: | 1998-2000 Chevrolet S-10 Pick Up and Blazer |
1999-2000 Chevrolet Silverado |
1998-2000 GMC Sonoma and Jimmy |
1999-2000 GMC Sierra |
1998-2000 Oldsmobile Bravada |
Equipped with 4.3L L35 only |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
The fuel gauge and temperature gauge are inoperative and the low fuel and battery lights are on. The PRNDL indicator is inoperative on A/T vehicles. These symptoms can be intermittent. When using a scan tool the inputs are normal when viewed on the powertrain data list, but read zeros when viewed in I/P data list. The gauges will sweep when using the scan tool. This can be caused by an open in circuit 241 to the VCM connector C4 pin 13. This is the ignition 3 feed to the VCM. It is one of the inputs used to determine the ignition lock/switch position. When this circuit is open the VCM sees the switch as always in the crank position, while in this mode the class 2 serial data is in a reduced function state, the Tech 2 will still communicate with the various modules and no DTCs will set.
The following is a matrix indicating what inputs are used to determine the ignition switch position at the VCM.
Position | Ignition 0 | Ignition 1 | Ignition 3 |
---|---|---|---|
Unlock | B+ |
|
|
Run | B+ | b+ | b+ |
Crank | B+ | b+ |
|
Check for B+ at VCM connector C4 pin 13, this circuit 241 should only have battery voltage when the ignition switch is in the run position.
Note: Both the 2 wheel drive and 4 wheel drive S/T vehicles with a 4.3 L engine use fuse #15 (4WD) in the IP fuse block and the related wiring (circuit 241) to the VCM for this crank input.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.