Transmission

P0702 — Transmission Control System Electrical Fault

Severity: medium Drive with care, to a shop

What P0702 means

P0702 means the transmission control module (or the engine computer, if it controls the transmission) detected an out-of-range electrical signal in the transmission control circuits. It is a general code that points to a power, ground, communication or module problem rather than one specific part. The transmission usually enters a protective limp mode.

Symptoms

  • Transmission warning light or Check Engine light on
  • No gear engagement or stuck in one gear
  • Harsh or delayed shifts
  • Transmission limp mode
  • U0101 (lost communication with the TCM) may appear alongside
  • Vehicle won't move when put in gear

Possible causes

  1. Blown fuse in the transmission control power circuit
  2. Poor power or ground at the transmission control module
  3. Damaged or corroded wiring and connectors at the transmission
  4. Fluid or moisture in the transmission connector or internal harness
  5. Failed transmission control module (TCM)
  6. Engine computer fault or communication errors between modules

How to diagnose

  1. Scan all codes, note the freeze frame data and look for communication codes such as U0101
  2. Check the fuses and relays that feed the transmission controls, using the wiring diagram
  3. Measure supply voltage and ground resistance at the control module connector
  4. Inspect the transmission harness and connectors for corrosion, chafing, fluid and bent pins
  5. Check transmission fluid level and condition
  6. Check battery voltage and charging system output
  7. Test wiring continuity from the module to the solenoids and sensors
  8. If power and wiring are good, test the module and reflash or replace it as needed

Common fixes

  • Replace the fuse after finding the cause of any short circuit
  • Restore power and ground, clean and treat corroded contacts
  • Repair or replace damaged wiring or a connector
  • Replace or reprogram the transmission control module
  • Fix fluid leaks into the connector and replace the fluid if needed

Questions and answers

What does P0702 mean?

It is a general electrical fault in the automatic transmission control system. The module saw an incorrect voltage or signal in its circuits, so the power, wiring and the module itself need to be tested.

Can I drive with a P0702 code?

Only briefly and carefully, to the nearest shop. The transmission may go into limp mode or stop engaging gears, so don't put off the repair.

Can I just clear P0702?

Clearing only hides it temporarily. If the cause is wiring, power or the module, the code will return and the transmission could fail at a bad time.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.