Trouble Code Diagnosis

MULTIPLE INTERMITTENT CODES

CIRCUIT DESCRIPTION
A damaged data line circuit or one of the components connected to the data line may cause multiple or intermittent setting of data line Codes B333, B334, B335. B336 and/or B337. When operating normally. the serial data line voltage should continually fluctuate from 0.1 to 5 volts.

If the serial data line has been shorted to ground. the voltage at the ALDL will be 0 volts. If it has been shorted to voltage. It will be over 5 volts. If one of the components on the serial data line is affecting the data line voltage, the serial data voltage at the ALDL connector will be a steady value anywhere between 0.1 and 5 volts.

CONDITION NOT PRESENT DIAGNOSIS

Condition Not Present
Sometimes the conditions can be duplicated by carefully warming the Data Line components with a heat gun and/or lightly tapping on them. If the condition cannot be duplicated on the vehicle during diagnosis, follow the procedure below:
1. Make sure that the grounds on the fender near the battery, are clean and tight. Make certain there are star washers on the studs and that the studs are free of corrosion.
2. Check the BCM EPROM and EEPROM and ECM CALPAK and PROM or MEM-CAL assembly for proper insertion into their respective sockets. Inspect components for bent or damaged legs.
3. Make sure both BCM and ECM have the correct PROMS for that model year.
4. If the source of the intermittent problem has not been found and the intermittent condition persists:
A. Verify good connections at the following components. Check each connection for proper latching and pins seated in the connector.
B. Replace the following components, one at a time, checking for reoccurrence of the intermittent condition after each component replacement. Follow the order listed. the order listed represents most likely to least likely cause of a multiple communications code condition:
- ECCP.
- BCM.
- PROGRAMMER.
- ECM.
- BCM EPROM.
- IPC.
- ECM CALPAK and EPROM.
- BCM EEPROM.

When all diagnosis and repairs are complete, clear codes and verify operation.