P0670 DTC Glow Plug Control Module Circuit Malfunction

OBD-II Trouble Code - P0670 - Data Sheet

P0670 - Glow Plug Control Module Circuit Malfunction

What does trouble code P0670 mean?

The OBD (On-Board Diagnostic) code P0670 is generic and covers all brands of latest diesel engines, including those used in Ford, Dodge, Chevrolet, GMC and VW Volkswagen vehicles. To understand the meaning of this code, its ramifications and symptoms, it is important to understand the dynamics at work.

Unlike a conventional gas engine, diesel does not rely on a compressed fuel mixture and an electrical ignition source. Diesels have a much higher compression ratio than gas ones.

This high compression ratio causes the air in the cylinder to heat up to over 600 degrees, which is enough to ignite the diesel fuel. When the piston reaches cylinder top dead center, high pressure fuel is sprayed into the cylinder. It ignites immediately when it encounters superheated air and the expanding gases push the piston downward.

Glow plug

Since the diesel engine requires overheated air to ignite the fuel, the problem occurs when the engine is cold. When starting a cold engine, it is difficult to overheat the air when its heat is quickly transferred to the cold cylinder head.

The glow plug is the solution. Installed in the cylinder head, the pencil-shaped candle heats up to XNUMX seconds until it glows. This raises the temperature of the surrounding cylinder wall, allowing the heat of compression to rise enough to ignite.

Typical Diesel Engine Glow Plug:

Glow plug chain

The circuit is common to all diesels except for the component used to measure the glow plug runtime. Either the car will have a glow plug control module or the PCM will do it. Instead of a service manual, just call your auto parts store and ask if they sell the control module. If not, then the computer adjusts the time.

• Batteries - Check batteries for full charge. The compressed air in the cylinders only retains heat for a fraction of a second, so the engine must spin quickly.
• Glow Plug Relay - Similar to the remote starter relay and is usually located next to the starter relay. They are not interchangeable because the glow plug relays are designed to handle a much higher amperage.
• Oil Temperature Sensor - Used by the PCM to determine when and how long the glow plugs are running.
• Glow Plug Fuse - The ignition switch supplies power to the glow plug relay while the PCM provides ground to operate it, or in the case of a module, it supplies ground
• Glow Plug Control Module or PCM

Work principles

When the ignition is on, it supplies power to the glow plug relay. The computer or control module will ground the relay to trigger it. The decisive factor is the oil temperature sensor. When the computer detects a cold engine, it activates the control module or relay to provide ground.

When activated, the relay supplies power to the glow plugs for a time determined by the computer or control module.

If the vehicle has a control module, all it does is simply ground the relay. It will have a fused power supply and the computer provides a ground connection to turn it on.

Symptoms

The glow plug warning light will illuminate and the engine will start slowly in warm weather or will not start in cold weather.

If the engine does start, an audible knocking will be heard until the engine is at operating temperature. White smoke will be visible from the tailpipe as excess fuel from the hard launch will burn. The engine will have a noticeable miss until the cylinder head temperature rises enough to maintain complete combustion.

The glow plug indicator lamp is on:

The most obvious problem with this code is that your diesel engine simply won't start. At the very least, he will most likely hesitate before reviving. Usually, if the weather is warm, even a P0670 code should not prevent your car from starting. However, if it's cold outside, you'll probably have a lot more trouble starting.

Even if the engine starts, you will most likely hear a very loud knock coming from it. This will continue until the engine has warmed up and is able to operate normally within acceptable operating temperatures.

White smoke can also come from your car's exhaust pipe. This is because a hard start produces excess fuel that needs to be burned. The engine will have a noticeable overshoot before the cylinder head temperature rises enough to support complete combustion.

Possible reasons

They have an expected life of 30,000 miles and have reached their useful life and need to be replaced. Incorrect injection timing will cause excessive wear to the glow plug. Next to changing time, a stuck glow plug relay or timer module will burn them out faster than a flea can jump on a slow moving dog.

One problem might just be GPCM itself. A failed GPCM will generate this code on its own. Other common problems that lead to code P0670:

• GPCM harness is shorted or open
• GPCM chain suffering from poor electrical connection
• ECM not working correctly (this is quite rare)

Diagnostic steps and possible solutions

• Start by checking a fully charged battery
• Check wiring for defects
• Use a voltmeter to check the battery voltage at the main power terminal of the glow plug relay. Ask an assistant to turn on the key and check the opposite terminal for voltage drops. If the voltage drop exceeds half a volt, replace the relay. The relay is the main cause of failure for this code.
• Check the power supply from the ignition switch to the relay with the key on.
• Check relay operation by disconnecting the oil temperature sensor and turning on the key. When activated, it will click. Remove grounding from the small relay terminal and connect it to ground. If it works now, then there is a problem with the module or PCM.
• Check the glow plugs for an open circuit. Disconnect the connector from the glow plugs. Connect a test lamp to the positive terminal of the storage battery. Touch each terminal of the glow plug. Everyone needs to show good soil. They can also be checked with an ohmmeter. Each must have less than 4 ohm resistance or very low resistance.

Other Glow Plug DTCs: P0380, P0381, P0382, P0383, P0384, P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678, P0679, P0680, P0681, P0682. P0683. P0684.

Common Mistakes When Diagnosing Code P0670

The biggest mistake mechanics make when this code is present is to replace the glow plug. Because this is the most obvious feature of the problem, many people assume that it just doesn't work. While a new glow plug may work better at first, if you don't fix the underlying problems, it's only a matter of time before you see a mechanic again.

How serious is the P0670 code?

Your life will not be in danger if code P0670 is stored. Also, it won't cause serious damage to your vehicle. However, until this problem is fixed, you will have terrible times with ignition. So, in this regard, this is a very serious matter that should be dealt with immediately.

What repairs can fix code P0670?

Your mechanic can do any of the following:

• Replace the battery
• Replace damaged wires or connectors
• Glow plug relay repair
• Replace the GPCM
• Replace PCM (this is the least likely solution)

Additional comments to consider regarding code P0670

Just because your diesel engine needs a couple extra seconds to start in cold weather doesn't mean your GPMC or the glow plug needs to be replaced or repaired .

What is P0670 Engine Code [Quick Guide]

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