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P0A04 Generic (SAE) Basic entry

Motor Electronics Coolant Temperature Sensor Circuit Intermittent

Updated 2026-10-02 · Hybrid propulsion

Severity
Medium
Typical repair cost
40 – 350 EUR
System
Powertrain

What it means

P0A04 is stored when the Motor Electronics Coolant Temperature signal drops out or jumps erratically for short periods. Intermittent faults are almost always connector, wiring or vibration related.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Hybrid system warning light
  • Reduced electric assistance or no EV mode
  • Vehicle may refuse to start (ready mode)
  • Higher fuel consumption

Common causes

  1. Damaged, chafed or corroded wiring in the Motor Electronics Coolant Temperature circuit
  2. Corroded, loose or water-damaged connector terminals
  3. Failed Motor Electronics Coolant Temperature component (sensor, solenoid or actuator)
  4. Poor ground connection for the module or component
  5. Faulty control module driver (rare, confirm all else first)

How to diagnose

  1. Read freeze frame data and note when the code set (cold start, under load, after rain)
  2. Inspect the Motor Electronics Coolant Temperature connector for bent pins, corrosion and water; wiggle the harness with the engine running and watch live data
  3. Measure supply voltage and ground at the connector with the key on
  4. Check the signal wire for shorts to ground or battery and for continuity to the control module
  5. Test or substitute the Motor Electronics Coolant Temperature only after wiring and connectors are confirmed good
  6. Clear the code and complete a drive cycle to confirm the repair

Frequently asked questions

Can I keep driving with P0A04?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing P0A04 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

P0A01P0A02P0A03

Nearby codes in this group