6.0L Power Stroke P0670: Causes and How to Fix It

A 6.0L Power Stroke P0670 code points at the glow plug module control circuit, the system that heats the cylinders for cold starting. On the 2003 to 2007 6.0L it usually shows up as hard cold starts, rough running and white smoke until the engine warms, and a glow plug or wait-to-start light that does not behave normally. The important thing to understand is that P0670 can be the glow plug control module itself, or a failed glow plug that damaged the module, so replacing one without checking the other is how people end up buying the same part twice. This guide covers what P0670 means on the 6.0 Power Stroke, the common causes, how to confirm, the fix, and how to prevent a repeat.

What 6.0L Power Stroke P0670 means

The 6.0 Power Stroke uses a glow plug control module, sometimes called the GPCM, to power the eight glow plugs on a controlled schedule for cold starting and cold running. The engine control module watches that circuit, and when it sees a fault in the module control circuit it sets 6.0L Power Stroke P0670. In plain terms, the computer is not seeing the glow plug system respond the way it should. That can be the module, the glow plugs it feeds, or the wiring between them. The code names the circuit, not the exact failed part, which is why you confirm before buying.

The common causes, in order

On the 6.0 Power Stroke, these are the usual causes of P0670, from most common to least:

• A shorted or failed glow plug: a glow plug that has shorted internally can overload and damage the control module, and it is a very common root cause. This is why you test the glow plugs, not just replace the module.
• Failed glow plug control module: the GPCM itself can fail electrically and set the circuit code.
• Wiring, connector, or ground problems: corrosion or a poor connection in the glow plug circuit produces a fault.
• Low system voltage: weak batteries or a charging problem can make the glow plug system behave abnormally.

How to confirm the cause before buying parts

Scan the glow plug data

With a capable scan tool, read the glow plug module data and any glow plug fault information. Codes that point at a specific glow plug or bank help narrow the search before you condemn the whole module.

Test each glow plug

This is the most important step. Measure each glow plug for a short or an open, because a shorted glow plug is a leading cause of P0670 and will take out a new module if you do not find it first. Never install a new module without confirming the glow plugs are healthy.

Inspect wiring, connectors, and grounds

Check the glow plug harness, connectors, and grounds for corrosion and damage. A poor connection can set the code without a bad module or glow plug.

Check battery and charging health

Confirm the batteries and charging system are strong, since low voltage can make the glow plug system behave erratically and muddy your diagnosis.

The fix

Repair the confirmed cause, and do it in the right order. If a glow plug is shorted or failed, replace the affected glow plugs, and many 6.0 owners replace the full set with a fresh harness while access is open, since the labor overlaps and mixed old and new glow plugs invite a repeat. If the module is confirmed failed, replace it, but only after the glow plugs are verified healthy so the new module is not immediately damaged. Repair any corroded wiring or grounds, and address weak batteries. Fixing the glow plugs and the module together, in that order, is what keeps 6.0L Power Stroke P0670 from coming right back.

Prevent it from coming back

Use quality glow plugs and replace them as a set so they age together, keep the harness and connectors clean and protected, and maintain strong, healthy batteries. Addressing a hard cold start early, before a glow plug shorts and takes the module with it, is the cheapest way to stay ahead of this code. A healthy glow plug system with good connections rarely throws P0670.

Shop the parts for this fix

When your testing calls for glow plugs, use a quality set with the harness the job needs. Our 6.0L Power Stroke glow plug kit with harness refreshes all eight and the wiring at once, and you can find glow plugs, harnesses, and related parts in our diesel glow plug parts section. If you are weighing the 6.0 against the other Ford diesels, our guide on the 6.0 vs 6.4 vs 6.7 Power Stroke puts its quirks in context. Match the part to the confirmed cause and the code stays gone.

Frequently Asked Questions

What does P0670 mean on a 6.0 Power Stroke?

It is a glow plug module control circuit fault. The engine control module sees a problem in the glow plug control system, which sets 6.0L Power Stroke P0670. It can be the module, a glow plug, or the wiring between them.

Is P0670 the glow plug module or the glow plugs?

It can be either, and they are related. A shorted glow plug can damage the module, so always test the glow plugs before replacing the module. If you install a new module without finding a bad glow plug, the new module can fail too.

Will P0670 keep my truck from starting?

It mainly affects cold starting and cold running, so the truck may start hard and run rough until warm, especially in cold weather. It is best to fix it before winter rather than rely on marginal cold starts.

How do I keep P0670 from returning?

Use quality glow plugs replaced as a set, keep the harness and connectors clean, and maintain strong batteries. Catching a hard cold start early prevents a shorted glow plug from taking the module with it.

Bottom line

A 6.0L Power Stroke P0670 code is a glow plug control circuit fault, and the key is to test the glow plugs before replacing the module, because a shorted glow plug is a common cause and will kill a new module. Confirm the glow plugs, the wiring, and the module in that order, fix what is confirmed with quality parts and a fresh harness, and keep the batteries strong, and the code will not return.