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2003 TOYOTA TACOMA
2.7L I4•RWD•AUTOMATIC•gas•3RZ-FE
5 active safety recalls on this vehicle — view recalls
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Repairs0Labor1066Torque2197Fluid17DTC3480Battery2Maintenance0Recalls5
P0688high severityPowertrain

ECM/PCM Power Relay Sense Circuit /Open

on 2003 Toyota Tacoma 2.7L I4 · RWD

What this code means

The PCM detects an open in the sense circuit used to monitor the ECM/PCM power relay output. The module cannot confirm relay power status.

Symptoms

  • Intermittent no-start
  • Stored power relay codes
  • Erratic startup behavior

Common causes

  • Open sense circuit wiring
  • Faulty power relay
  • Corroded connector pins
  • PCM fault

Diagnostic steps

  1. Inspect sense circuit for open
  2. Test relay output voltage
  3. Check connector and pin integrity
  4. Verify PCM sense input
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