MIL ON Erroneous DTCs 33/43 Trans in Backup Mode

BULLETIN NUMBER
SB94-05-003

ISSUE DATE
DECEMBER 1994

GROUP
TRANSMISSION

4L30-E A/T PHANTOM DIAGNOSTIC TROUBLE CODES

AFFECTED VEHICLES

All Trooper (KT), Trooper (UX), and Rodeo (UC) V6 models equipped with 4L30-E automatic transmissions and Bosch Transmission Control Modules (TCM).

SERVICE INFORMATION

When the engine is first started, especially in cold weather conditions or after long periods of inactivity, a voltage drop from the battery (an output less than 10.5 volts) can cause the TCM to set erroneous or "phantom" diagnostic trouble codes (DTCs 33 and/or 43) or no code, which will flash the CHECK TRANS light continuously and switch the transmission into backup mode. This Service Bulletin provides guidelines to check for phantom DTCs when the CHECK TRANS indicator lights under these conditions.

^ PHANTOM TROUBLE CODES CHECK

1. Before suspecting a transmission or TCM problem, make sure that the battery is in good working condition. Load test the battery and verify that all connections are intact and are not damaged (i.e., loose, damp, or corroded). Ensure that the battery recovers to at least 10.5 volts immediately after the engine is started. If the battery does not recover to 10.5 volts, and the charging system is functioning correctly, the battery must be replaced.

2. Clear the diagnostic trouble codes from the TCM and retest the vehicle.

3. Should any of the conditions reappear (i.e., DTC 33 and/or 43, or no code), proceed with troubleshooting procedures called out in the appropriate Workshop Manual. Make the following checks prior to any troubleshooting action:

A. Check the force motor resistance.

NOTE
Resistance must read between 3.5 and 6.0 ohms at ambient temperature (68°F). If the fluid temperature is higher, the force motor resistance will be higher, up to 20% higher at 176°F.

1). If the resistance is too high, check the force motor connectors to ensure that the pins are not corroded.

2). If the problem is intermittent, make certain that all connectors are in good condition (i.e., not loose, damp, corroded, or damaged).

3). If the connectors are defective, repair/replace, as necessary.