What Does P0702 Mean?
The TCM or ECM has detected an electrical fault in the transmission control system. This code specifically indicates a range or performance issue with the transmission control system's electrical circuits, which may involve the TCM power supply, ground, or internal processing. The driver may notice the vehicle stuck in limp mode, delayed gear engagement, or the inability to shift out of a single gear.
Common Causes
30%
TCM power supply or ground circuit fault — poor connection, blown fuse, or corroded terminals
25%
TCM internal electronics failure
20%
Wiring harness damage between the TCM and transmission solenoid/sensor pack
15%
Faulty transmission range sensor or gear position input to TCM
10%
CAN bus communication fault between ECM and TCM
Diagnostic Steps
1
Check all TCM-related fuses and relays — verify the TCM power supply fuse is intact and the relay is clicking and providing voltage.
2
Measure voltage at the TCM connector pins — verify battery voltage at the power pins and less than 0.1V drop on the ground pins. Compare readings to the wiring diagram for the specific vehicle.
3
Inspect the transmission external wiring harness and connector for water damage, corrosion, or broken pins — especially on vehicles where the TCM or connector is located in a splash zone.
4
Check CAN bus communication by monitoring for U-codes (communication fault codes) in both the ECM and TCM. A CAN bus issue will prevent proper data exchange between modules.
5
If TCM replacement is needed, ensure the new module is programmed with the correct calibration for the vehicle's transmission type, axle ratio, and tire size.
Estimated Repair Cost
$200 - $2,500
Parts + labor, varies by vehicle and location
The TCM or ECM has detected an electrical fault in the transmission control system. This code specifically indicates a range or performance issue with the transmission control system's electrical circuits, which may involve the TCM power supply, ground, or internal processing. The driver may notice ...
The most common cause of P0702 (Transmission Control System Range/Performance) is: TCM power supply or ground circuit fault — poor connection, blown fuse, or corroded terminals
Typical repair costs for P0702 range from $200 to $2,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle may be stuck in limp mode or have severely limited transmission functionality. Driving is possible at reduced speed but should be limited to reaching a repair facility. Loss of TCM control can result in unexpected gear changes or inability to shift, which poses a safety risk in traffic.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0702 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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