What it means
A general electrical fault is detected in the transmission control system. The TCM has flagged a circuit problem (open, short, or supply issue) without specifying which component. Look up additional codes from the TCM for detail.
At a glance
- Usually lights the check-engine light
How it works
The transmission control system depends on electrical power, grounds, wiring, and circuits to operate the transmission and exchange control signals. P0702 indicates a general electrical fault in that system; it does not name the failed circuit, so additional TCM codes are needed to locate it.
Common causes
Most likely first.
- Open or short in transmission control wiring
- Poor connector contact or corroded terminals
- Low or unstable power or ground to the TCM
- Fault in a transmission control circuit or component
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Read codes from the TCM and PCM, including freeze-frame data, to identify any named circuit or supply fault recorded alongside P0702.
- Check battery condition and charging-system operation, since unstable vehicle voltage can disrupt transmission control.
- Inspect TCM and transmission connectors, fuses, wiring, and grounds for corrosion, loose terminals, chafing, or damage.
- Test TCM power and ground under the conditions specified by the manufacturer, then check the circuits named by any companion codes.
- If power, grounds, and wiring are sound, diagnose the implicated transmission control component or module using the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose TCM and transmission connectors.
- Repair damaged transmission-control wiring or a poor ground connection.
- Replace a failed fuse or correct a verified power-supply fault.
- Repair or replace a transmission control circuit component confirmed faulty by testing.
- Replace the TCM only after its power, ground, and external circuits have been verified.
Can I keep driving?
If the transmission shifts normally, drive only as needed until the electrical fault is diagnosed. Avoid long trips and stop if the vehicle loses drive, shifts unpredictably, or enters limp mode, because a control or supply fault can leave it stuck in a gear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.