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DTC codes / P06xx · Computer and output circuits / P067A

P067ACylinder 4 Glow Plug Control Circuit Low

P067A means the engine computer has detected an abnormally low voltage or current draw on the glow plug control circuit for cylinder 4. The computer expects a certain electrical load when it commands that glow plug on, and the low reading tells it the circuit is not working as designed, which can prevent that cylinder from cold-starting smoothly.

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

Symptoms you may notice

  • Illumination of the glow plug or check engine light, often with no other symptoms besides the warning light
  • Rough idle or misfire immediately after a cold start that improves as the engine warms
  • Extended cranking time before the engine fires in cold weather
  • White or blue smoke from the exhaust during cold running
  • Slightly reduced fuel economy or increased emissions during warm-up
  • A stored pending or history code that returns after clearing if the fault is intermittent

Common causes, most likely first

  1. Failed glow plug on cylinder 4 with an open or high-resistance element
  2. Damaged, corroded or disconnected electrical connector at the cylinder 4 glow plug
  3. Broken or chafed wire in the glow plug harness between the control module and the plug
  4. Faulty glow plug control module output for that cylinder
  5. Poor engine or chassis ground connection affecting the glow plug circuit
  6. Water or oil intrusion into the glow plug connector or harness
  7. Incorrect glow plug installed previously with the wrong resistance specification

How to diagnose and fix it

  1. Clear the code and verify whether it returns immediately or only after a cold-soak, which separates a hard fault from an intermittent one
  2. Inspect the cylinder 4 glow plug connector and harness for corrosion, looseness, chafing or oil intrusion
  3. Measure the resistance of the cylinder 4 glow plug and compare it with the other cylinders to identify an outlier
  4. Check the glow plug control module output and the circuit voltage drop with a multimeter or oscilloscope while commanding the glow plug on
  5. Verify engine and chassis grounds are clean and tight, especially any ground shared with the glow plug control module
  6. Replace the faulty glow plug if resistance is out of specification, using the correct part for the engine
  7. Repair or replace damaged harness sections or the glow plug control module if the circuit tests good but the code persists

What a low glow plug code really means

  • A low circuit code does not automatically mean the glow plug itself has failed, because a poor connection or a faulty control module output can produce the same low-current reading.
  • Technicians often replace all glow plugs when only one is faulty, but the code is cylinder-specific and the other plugs may be perfectly serviceable.
  • The glow plug control module may command a brief self-test at key-on, so a code can set without the engine ever being cold-started.
  • A glow plug with the wrong resistance specification can set this code even though it physically fits and heats up, so always compare against the correct part number.
  • Intermittent low-circuit codes frequently trace to a chafed harness near the engine cover or a connector that wicks oil, not to the glow plug element.

Can I keep driving with P067A?

You can usually drive the vehicle, but cold starting may be rough and extended cranking can stress the starter and battery. Avoid repeated long cranking attempts and have the circuit checked before cold weather makes the fault worse.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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