P06F7

What it means

P06F7 means the engine control unit has detected a low voltage on the control circuit between itself and glow plug control module 2. The control unit commands the module and monitors that circuit, and it saw a voltage lower than expected, such as a short to earth or a weak or open signal. Which cylinders module 2 serves depends on the engine, so check the model-specific wiring information.

Symptoms

• Engine management light on
• Hard or extended cranking on cold starts
• White or grey smoke after a cold start
• Rough running or misfire when cold
• Glow plug warning light flashing or staying on
• Slightly higher emissions or fuel use on cold running

Possible causes

• Wiring fault in the control circuit to glow plug control module 2, such as chafed insulation shorting to earthlikely
• Corroded, loose or damaged connector at the glow plug control module or the engine control unitlikely
• Faulty glow plug control module 2 pulling the control line low internallylikely
• Poor power or earth supply to the module, for example a corroded earth point or weak batterypossible
• Water ingress or heat damage to the module or its harness, depending on where it is mounted on that enginepossible
• Fault inside the engine control unit driver for that circuitrare
• Outdated or faulty control unit software where the manufacturer has documented it as a cause for this enginerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine temperature, battery voltage and whether other glow plug or module codes are present
2. Check battery condition and charging voltage, as low supply voltage can upset module communication and control signals
3. Visually inspect the harness and connectors for glow plug control module 2, looking for chafing, melted insulation, green corrosion, water and bent or pushed-back pins
4. Check the module's power and earth supplies with a multimeter, including voltage drop under load
5. Using the wiring diagram for the specific engine, test the control wire for short to earth and continuity back to the engine control unit with the connectors disconnected
6. Use a scan tool to command or monitor the glow plug system if supported, and compare live data for module 1 and module 2
7. Check the signal at the control unit with a multimeter or oscilloscope during a glow cycle to see whether the line is being held low
8. Check for any manufacturer service information or software updates relating to this code on the specific model

How to fix

• Repair or replace the damaged section of wiring, using proper soldered and sealed joints or a new harness section
• Clean, repair or replace corroded or damaged connectors and terminals
• Replace glow plug control module 2 if it is confirmed faulty after supply, earth and wiring checks
• Repair poor earth or power supply connections and correct any battery or charging faults
• Dry out and seal any water ingress point, then replace affected components
• Apply an updated control unit calibration only if the manufacturer lists an outdated one as a known cause for this engine

Can I keep driving?

Nearby codes

• P06F6GenericGlow Plug Control Module 2 Control Circuit/Open
• P06F8GenericGlow Plug Control Module 2 Control Circuit High