Fuel - Cranks But Doesn't Start or Immediately Stalls

File in Section: 6E - Engine Fuel & Emission

Bulletin No.: 77-65-31

Date: February, 1998

Subject:
Vehicle Cranks But Does Not Start, or Starts and Immediately Stalls, Vehicle Theft Deterrent PASSLOCK Security Light May Be Illuminated, No DTC's or Possible DTC P1626, P1630, P1631 Stored (Perform Diagnostic Procedures)

Models:
1998 C, K, G Models - with 6.5L Diesel Engines
(VINs S, F - RPOs L56, L65, L65-CMT)

Condition

Some owners of 1998 trucks equipped with the 6.5L diesel engine may comment on an engine no start or engine starts and immediately stalls. In addition, the vehicle theft deterrent system (PASSLOCK) security light may be illuminated. The vehicle may not have any DTC's or possible DTC's P1626, P1630, P1631 stored.

Do not replace the fuel injection pump for this condition.

Cause

The vehicle theft deterrent system (VTD), PASSLOCK, may have disabled the fuel system of the vehicle. For the 1998 model year, GM trucks are equipped with the VDT system called PASSLOCK. If a fault occurs in the VTD system, the PCM will not receive the correct serial data from the PASSLOCK module. Without the correct data, the PCM will not allow the fuel injection pump to deliver fuel. The vehicle theft deterrent system security light may be illuminated and the vehicle will not start, or start and immediately stall.

Correction

Always perform an on board diagnostics (OBD) system check on the vehicle prior to any repairs. The OBD system check will help determine if a fault exists in the VTD system, and if the VTD system is responsible for the no start condition.

Several different situations may be experienced when diagnosing the PASSLOCK VDT system. It is possible to monitor the operation of the VTD system using the Tech 2. It is also possible under certain circumstances to have an active PASS LOCK VTD system (fuel disabled) and set no DTC's.

If the engine cranks but does not start, or starts and immediately stalls, use the Tech 2 to check for DTC's in each of the following two areas:

1. Each subsystem in the Tech 2 (Powertrain or body)

2. Class 2 DTC's (Under Class 2 diagnostic circuit check, which will display all codes)

The following DTC's may be present in PASSLOCK fault detection:

P CODES (Powertrain) P1626, P1630, P1631

B CODES (Body) 80688, B2947, B2948, B2957, B2958, B2960, B3031, B3033

C CODES (Chassis) C0599

U CODES (Communication, listed at the end of the P codes, Section 6, Book 4 and Section 9D, Book 1) U1016, U1026, U1192, U1255

If no DTC's are set, pursue the following Tech 2 diagnostic path:

1. Powertrain

2. Engine Data List 1 (Engine list number may vary by vehicle line)

3. Data list parameter: VTD fuel disabled "ACTIVE"

If the word active is present during or immediately following cranking, a PASSLOCK fault exists (inactive indicates a properly operating PASSLOCK system). Note that the Tech 2 parameter may revert to inactive and the security light will stop flashing approximately 5 seconds after the key is released from the crank position. Watch the Tech 2 parameter while cranking or immediately after releasing the key. If a PASSLOCK fault is present, discontinue all Powertrain diagnostics and refer to the vehicle theft deterrent system diagnostics in the proper vehicle line Service Manual. For example, the C/K truck OBD system check for the 6.5L diesel is located on Page 6-2334 in Book 4. If DTC's are set, refer to the applicable chart. The VTD diagnostics are located in Section 9D or Book 1.

An alternative method of diagnosing PASSLOCK is to use the following Tech 2 diagnostic path:

1. Body system

2. Data list

3. Data list parameter: PASSLOCK code "OPEN" If the word open exists under this parameter, a PASSLOCK fault exists and the module is not receiving a message from the hall sensor. The vehicle will not start. The message "VALID CODE 1" (or 2, 3, etc. up to 10) will be displayed when the PASSLOCK module is receiving a valid message from the hall sensor.

Either of the above diagnostic methods may be used to determine PASSLOCK system status even it no DTC's are set.

Refer to the appropriate vehicle line Service Manual for additional diagnostic information on the PASSLOCK system or call the applicable divisional Technical Assistance Center.