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P0383 OBD-II Trouble Code: Glow Plug Control Module Control Circuit Low

check engine light

P0383 code definition

The PCM stores the P0383 code when a low voltage reading of the glow plug heater circuit is detected. This will often be accompanied by other glow plug circuit codes.

What the P0383 code means

In order to begin combustion in cold temperatures, the engine requires the heat provided in part by the glow plug system. The temperature and voltage of the glow plugs is monitored by the ECM before and during engine combustion. If the voltage reading detected by the ECM is more than 10% lower than the reading recommended by the manufacturer, the PCM will store the P0383 code.

What causes the P0383 code?

Faulty glow plugs are most commonly to blame for the P0383 code. However, there could be quite a few other causes, including:

  • Faulty glow plug relay
  • Bad glow plug module or timer
  • Open or shorted glow plug wiring harness
  • Blown fuses (which indicate an underlying issue elsewhere)
  • Loose, corroded, or shorted glow plug circuit electrical connectors
  • Loose, shorted, or open wiring in the glow plug heater circuit

What are the symptoms of the P0383 code?

A slow start, and possibly even white smoke from the exhaust when the vehicle does start, may be observed with the P0383 code. The engine may seem far too loud, and the glow plug indicator lamp may stay on constantly. The code will be stored in the PCM, and the Check Engine lamp will illuminate.

How does a mechanic diagnose the P0383 code?

After an OBD-II scanner detects the P0383 code, a technician should inspect of all the wiring and electrical components related to the glow plug heater circuit. Any damaged elements should be repaired or replaced. They should then clear the code and perform a test drive, checking that the Check Engine light does not reappear. If the light does reappear, the mechanic should check individual glow plug connectors for the proper voltage and ground signals.

As the mechanic moves through each potential repair to find the issue, they should be sure to clear the code from the PCM and retest the system after each step. This will ensure that the proper repair is performed, and that the issue will not reappear later.

Common mistakes when diagnosing the P0383 code

Many technicians report that the glow plug timers and glow plug relays are often replaced when they don’t need to be. Mechanics should be sure to check wiring and commonly at-fault parts before replacing anything, especially because the glow plugs themselves, or the electrical components, are most often to blame.

How serious is the P0383 code?

This issue can cause major issues with the start up and operation of a vehicle, especially in cold climates. If the P0383 code is stored in the PCM, the vehicle should be repaired right away.

What repairs can fix the P0383 code?

There are many ways that a technician can address a P0383 code detection. They include:

  • Replacing a faulty glow plug
  • Replacing a faulty glow plug relay
  • Repairing loose, shorted, or open wiring in the glow plug heater circuit
  • Replacing blown fuses, and searching for and repairing the underlying issue that a blown fuse can indicate
  • Replacing a bad glow plug module or timer
  • Repairing an open or shorted glow plug harness
  • Repairing loose, corroded, or shorted glow plug circuit electrical connectors

Need help with a P0383 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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