P0670
Glow Plug Module Control Circuit
- Severity
- Low
- Driving
- Drivable — book it in
A fault in the glow plug control module circuit. This module switches the heavy current the glow plugs need, and the engine module controls it. With the circuit faulty none of the plugs will heat, so cold starting suffers even if every plug is perfect.
Possible causes
- CommonFailed glow plug
- CommonCorroded connection at the plug
- CommonFailed glow plug control module
- PossibleDamaged wiring in the glow plug harness
- PossibleBlown fuse or fusible link
- PossibleSeized plug damaged during a previous removal
- CommonWiring fault between the engine module and the glow plug module
What you might notice
- Hard starting when cold
- White smoke on a cold start
- Rough running for the first minute from cold
- Glow plug light behaving oddly
- No symptom at all in warm weather
What to check, in order
- Test on a genuinely cold engine. In summer a diesel will often start acceptably with several dead glow plugs, which is why these faults go unnoticed until the first frost.
- Measure each glow plug individually. They fail one at a time, and the code may be set by just one of them.
- Inspect the connections at the plugs for corrosion - they sit in a hot, dirty part of the engine.
- Check the fuse or fusible link and the control module.
- Be aware that seized glow plugs are common on high-mileage engines and can break off during removal, which turns a cheap job into an expensive one. Worth knowing before starting rather than halfway through.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Computer output circuits and control module
P0600P0601P0602P0603P0604P0605P0606P0607P0608P0609P0610P0611P0612P0613P0614P0615P0616P0617P0618P0619P0620P0621P0622P0623P0624P0625P0626P0627P0628P0629P0630P0631P0632P0633P0634P0635P0636P0637P0638P0639P0640P0641P0642P0643P0644P0645P0646P0647P0648P0649P0650P0651P0652P0653P0654P0655P0656P0657P0658P0659P0660P0661P0662P0663P0664P0665P0666P0667P0668P0669P0670P0671P0672P0673P0674P0675P0676P0677P0678P0679P0680P0681P0682P0683P0684P0685P0686P0687P0688P0689P0690P0691P0692P0693P0694P0695P0696P0697P0698P0699