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P0670 is a diagnostic trouble code (DTC) for "Glow Plug Module Control Circuit". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
If your vehicle’s ECM detects a problem with the Glow Plug Control Module (GPCM) control circuit, this code gets stored.
Unlike gas engines, diesel engines don’t use sparkplugs for ignition. Instead, they rely on glow plugs for this important task. As the name would suggest, the Glow Plug Control Module is a big part of this. If it isn’t working correctly, your engine may not start.
One problem could simply be the GPCM itself. A defective GPCM will set off this code all on its own. Other common issues that lead to a P0670 code are:
The most obvious problem related to this code is that your diesel engine simply won’t start. At the very least, it will most likely hesitate before coming to life. Usually, if the weather is warm, even a P0670 code shouldn’t stop your vehicle from starting. However, if it’s cold out, you’ll probably have a lot more trouble getting going.
Even if the engine does start, you will most likely hear a very loud knocking noise coming from it. This will continue until the engine warms and is able to function normally within an acceptable operating temperature.
White smoke may also come out of your vehicle’s exhaust. This is because the hard start produces excess fuel that must be burned off. The engine will have a noticeable miss before the cylinder head temperature increases enough to sustain total combustion.
First, your mechanic will use their OBD-II scanner to diagnose which codes have been stored. Then, they’re going to check to see if your battery is working. Next, they’ll inspect the wiring, looking for any defects that may lead to the GPMC not getting the power it needs to work properly. A voltmeter helps with this.
After all that, they’re going to check to see if the ignition switch delivers power. They’ll do the same with the relay actuation by unplugging the oil temperature sensor and then hitting the ignition.
The biggest mistake mechanics make when this code is present is going right to replacing the glow plug. As it’s the most obvious feature of the problem, many people assume it’s simply not working. Although a brand new glow plug may function better at first, if you don’t address the underlying problems, it will only be a matter of time before you need to see a mechanic again.
Your life won’t be in danger when the P0670 code is stored. Likewise, it’s not going to lead to any serious damage to your vehicle. However, until this problem is fixed, you are in for a terrible time with your ignition. So, in that regard, this is a very serious issue that should be addressed right away.
Your mechanic may do any of the following:
Just because your diesel engine needs a couple extra seconds to start in the cold doesn’t mean your GPMC or glow plug need to be replaced or repaired.
At YourMechanic, we have an army of certified mobile mechanics ready to rescue you from the P0670 code and all kinds of other problems that can impact your vehicle. All you have to do is fill out this online form and we’ll quickly reply with a quote before scheduling an appointment. You can also call 1-800-701-6220 to speak with a service advisor about a good time and date for repairs. Our mechanics will happily meet you at your home or workplace.