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Vehicle engine and/or automatic transmission

Code: P0670 - The Glow Plug Control Module (controls diesel engine start-up) has an electrical problem or open circuit, which may affect engine starting in cold conditions.

When I see the p0670 code pop up, I know the vehicle’s PCM-basically the main computer-has picked up on a problem with the glow plug control module or its wiring. From years of wrenching on diesels, I can tell you that the glow plug system is absolutely critical for easy starting, especially if you live where winter really bites. The control module acts as the brains for the glow plugs, switching them on and off depending on how cold it is. If there’s a break in the circuit, a loose connection, or if the module itself is on the fritz, the PCM throws this code. Missing out on that pre-heating means your diesel’s going to fight you every step of the way on a cold morning. Trust me, you don’t want that struggle.

Causes of obd code P0670

From experience, the most common reasons I see for P0670 are:

A failed glow plug control module-this is the part that manages when the glow plugs turn on and off.
Faulty glow plugs themselves-sometimes one or more plugs just give out.
Problems in the wiring or connectors-damaged wires, corroded terminals, or loose connections can all break the circuit.
In rare cases, a problem with the PCM (the vehicle’s main computer) can be the culprit, but that’s not usually the first thing I’d suspect.

Most often the issue is with the module or the wiring, so that’s where I recommend starting your checks. This error can also happen on these car brands: Ford, Renault.

Symptoms of P0670 code

Let me walk you through what you’ll usually run into with a P0670. First thing, the check engine light comes on-sometimes that’s your only clue until the weather turns cold. Next, if you’re struggling to get the engine to fire up on chilly mornings, that’s a classic sign. I’ve had customers say the engine just cranks and cranks until they’re about ready to give up. Once it does start, you might notice a rough idle, a bit of knocking, or the engine just sounds off. Another giveaway? White smoke puffing out the exhaust after startup-that’s raw diesel not getting burned. And don’t be surprised if the engine feels really down on power until it gets some heat in it. These are all red flags your glow plug system isn’t doing its job.

Diagnosis steps for obd2 code P0670

When I’m tracking down a P0670, here’s how I go about it, step by step:

Always start by scanning for codes and clearing them. Sometimes, a one-off electrical hiccup can set a code that never comes back.
Next, I do a visual check of the glow plug control module and its wiring. I’m talking burnt spots, frayed wires, or crusty connectors-any of those will give you trouble. Don’t skip the grounds; a bad ground can cause all sorts of weirdness.
If nothing jumps out, I grab my multimeter and check for power and ground at the module itself. No power? Time to chase that circuit back and see where the juice stops.
Then I move on to the glow plugs. I test each one for continuity. Even a single bad plug can toss this code, so don’t assume they’re all good.
If the wiring and glow plugs are in the clear, I put the module under the microscope. Sometimes you’ll need a decent scan tool that can command the glow plugs on and off to check if the module’s listening.
And if I’ve checked all that and still come up empty, only then do I start thinking about the PCM. That’s a rare one, but it happens.

Here’s a pro-tip from the garage: Have someone wiggle the connectors while you watch your meter. Intermittent faults love to hide until there’s a little movement. Oh, and always double-check that your battery is fully charged before you start-low voltage can throw you off track.

Common mistakes when fixing P0670 engine code

A classic mistake I see is folks rushing out to replace the glow plug control module first thing, without even glancing at the wiring or testing the plugs. That’s a quick way to throw money down the drain. Another thing that gets overlooked way too often? Corroded connectors and loose grounds. These small details can be the root of big headaches. Don’t just check one plug and call it good-test every single one. Skipping these steps almost always leads to unnecessary part swapping and a lot of frustration in the end.

Seriousness of dtc P0670

Here’s the bottom line: ignoring a dtc p0670 can leave you stranded when you least expect it, especially if Jack Frost is knocking at your door. Diesel engines aren’t forgiving when it comes to cold starts without a working glow plug system. Keep pushing it and you risk more than just hard starts-you’re looking at extra strain on the starter, draining the battery, and potential damage to the exhaust from all that unburned fuel. I’ve seen folks wear out their starters or even damage the glow plugs further by ignoring this code. Don’t let a small problem turn into a much bigger repair bill.

Repair guide for P0670 trouble code

Once you know what’s causing your obd p0670, here’s what usually gets it sorted:

If you’ve got a bad glow plug control module, swap it out-OEM parts are the safest bet for reliability.
Found damaged wires or sketchy connectors? Repair or replace them, and be sure to clean off any corrosion. Tight connections are a must.
Bad glow plug? Change it with the correct one for your engine. Don’t mix and match here; use what’s specified.
If it turns out the PCM is the culprit (it’s rare, but it happens), you might need to reprogram or replace it-but that’s a last-ditch move.

After you’ve made repairs, clear the code and run the system through its paces to make sure everything’s working right. If you’re working on a Renault, heads up: some of their wiring layouts can make things a bit more fiddly, so take your time and double-check your work.

Conclusion

If there’s one thing I’ve learned over the years, it’s that letting a dtc p0670 renault or any p0670 code slide is just asking for trouble. A healthy glow plug circuit is what keeps your diesel starting strong and running smooth when the temperature drops. Take the time to check the wiring, test every plug, and only replace the module if you’re sure it’s to blame. Fix it right, and you’ll save yourself a whole lot of headaches-and probably a tow bill, too. Stay on top of it, and your diesel will reward you with years of reliable service.

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