P06FD: Glow Plug Control Module 2 to PCM Communication Range or Performance

What it means

The powertrain control module monitors communication with glow plug control module 2 and checks whether its messages and responses are within the expected range. It sets this code when that communication is missing or abnormal; the code alone does not identify the cause or imply a particular network fault.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Glow Plug Control Module 2 manages diesel glow-plug preheating and exchanges status messages with the PCM. P06FD means the PCM found that this communication was missing or outside its expected range or performance; the code alone does not identify the cause or prove a specific network fault.

Common causes

Most likely first.

1. Protocol mismatch
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Glow plug warning light on (often orange coil symbol)
• Hard cold start or no start in cold weather
• White smoke from exhaust during warm-up

How to diagnose it

1. Read freeze-frame data and codes from the PCM, Glow Plug Control Module 2, and other network modules to identify when the abnormal messages occurred.
2. Compare the reported module status and communication data with the manufacturer's diagnostic information, noting whether the fault is constant or intermittent.
3. Inspect the module connectors and communication wiring for damage, corrosion, loose terminals, or signs of a recent repair that could affect compatibility.
4. Check module power and ground, then test the communication circuit and network for wiring faults using the manufacturer's procedure.
5. If wiring and supplies are sound, verify gateway routing and module protocol or configuration compatibility, and check CAN termination against the manufacturer's specification.

Common fixes

• Secure or clean a poor connector contact at Glow Plug Control Module 2 or the PCM.
• Repair damaged communication wiring or restore a reliable module power or ground connection.
• Correct gateway routing or module configuration if diagnosis confirms a mismatch.
• Repair a CAN termination fault if it falls outside the manufacturer's specification.
• Replace a module only after confirming the fault follows that module and the network and configuration are correct.

Can I keep driving?

If the vehicle starts and runs normally, limit driving to necessary trips and be prepared for hard starting, especially in cold weather. A failed preheat may cause a no-start or white smoke during warm-up; address the fault before depending on the vehicle in cold conditions.