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DTC codes / P06xx · Computer and output circuits / P069B

P069BCylinder 9 Glow Plug Control Circuit High

P069B is a generic powertrain code indicating that the engine control module (ECM) has detected a high-voltage condition on the glow plug control circuit for cylinder 9. The ECM monitors the circuit and expects a certain voltage drop when the glow plug is commanded on; a reading above the expected threshold triggers this code.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp).
  • Often no symptoms besides the warning light, especially in warm weather.
  • Hard starting or rough idle when the engine is cold.
  • Excessive white smoke from the exhaust after a cold start.
  • Reduced fuel economy during warm-up.
  • Possible glow plug-related diagnostic trouble codes stored for other cylinders.

Common causes, most likely first

  1. Faulty glow plug on cylinder 9 (open circuit or high resistance).
  2. Damaged or corroded wiring or connector at the cylinder 9 glow plug.
  3. Open or high-resistance circuit in the glow plug control module or wiring harness.
  4. Failed glow plug control module (GPM) or relay.
  5. Poor ground connection for the glow plug circuit.
  6. ECM software issue or internal fault (rare).

How to diagnose and fix it

  1. Perform a visual inspection of the cylinder 9 glow plug, connector, and wiring for damage or corrosion.
  2. Check the glow plug resistance with a multimeter and compare to specifications; replace if out of range.
  3. Test the glow plug control circuit for voltage drops and continuity from the ECM to the glow plug.
  4. Inspect and clean the glow plug ground connections.
  5. Test the glow plug control module or relay according to the manufacturer's procedure.
  6. Repair or replace any damaged wiring or connectors.
  7. Clear the code and verify the repair with a test drive; reprogram the ECM if necessary.

Glow Plug Circuit High: Don't Just Replace the Plug

  • A high-voltage code often results from an open circuit, such as a broken wire or unplugged connector, rather than a failed glow plug itself.
  • Corrosion at the glow plug connector is a common cause that can mimic a faulty glow plug and is easily overlooked.
  • The glow plug control module may set this code if it detects an open circuit, even when the glow plug is good.
  • Always check for related codes for other cylinders; multiple high-voltage codes may point to a shared power or ground issue.
  • After repairs, the ECM may require a relearn procedure or several drive cycles before the code clears permanently.

Can I keep driving with P069B?

You can generally drive the vehicle with this code, but cold starting may be difficult and prolonged driving with a faulty glow plug can lead to additional wear. Avoid heavy loads and long idling until the repair is completed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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