P1739 (76) - Power-Up at Speed

Name of Code:
P1739 (76) - Power-Up at Speed

When Monitored:
When TCM (Transmission Control Module) initially powers-up.

Set Condition:
If the TCM powers up and senses a valid forward gear PRNDL code and the output RPM is above 800 RPM (approx. 20 MPH) the code will be set.

Theory of Operation:
If a vehicle loses power to the TCM, the solenoids will go to their respective power off state. Some solenoids are normally vented and some are normally applied in their power off state. The transmission is designed to be in 3rd gear with all of the solenoids in this state. However, if power is restored, the TCM will power-up and normal operation will be restored.

This code identifies that power to the TCM was restored when the gear selector was in a "Drive" position while the vehicle was moving at speeds above 20 MPH. This code does not indicate a problem with the transmission or TCM, instead, it suggests intermittent problems in the fused ignition switch output, fused B (+), or ground circuits to the TCM. Alternately, if a person performs a rolling restart maneuver, the code can be set. Therefore it is critical that this DTC be investigated if the vehicle is experiencing intermittent 3rd gear operation and a subsequent return to normal operation. Transmission Effects: No limp-in, although the symptom might be described as an intermittent limp-in. Code is for information only when trying to diagnosis intermittent 3rd gear operation and a subsequent return to normal operation.

Possible Causes:
- No Problem if vehicle is started in "neutral" at speeds above 20 MPH and shifted quickly to a forward gear position.
- Quick key off then on while driving is any forward gear.
FOR INTERMITTENT 3rd GEAR OPERATION AND THEN A SUBSEQUENT RETURN TO NORMAL OPERATION WITHOUT CYCLING THE IGNITION KEY
- Intermittent Direct Battery (Fused B (+)) connection between TCM (60-way pin 56) and battery.
- Intermittent Fused Ignition Switch Output between TCM (60-way pin 11) and ignition switch.
- Intermittent Ground to TCM (60 way pins 53 and 57).