P0383 OBD II Trouble Code Glow Plug Control Module Circuit Low
How to quickly diagnose, repair, and info on symptoms and causes of a P0383 code that indicates a low circuit condition in the glow plug control module.
Symptoms of P0383 OBD II Trouble Code
Batteries - Check the batteries for a full charge. The compressed air in the cylinders only retains its heat for a faction of a second so the engine must turn over rapidly
Glow Plug Relay - Appears similar to a remote starter relay and is usually located next to the starter relay. The two are not interchangeable because the glow plug relay - by design - handles much higher amperage
Oil Temperature Sensor - This is used by the PCM to sense when and how long to operate the glow plugs
Glow Plug Fuse - The ignition switch supplies the power to the glow plug relay while the PCM computer supplies the ground to actuate it, or in the case of a module, it will supply the ground
Glow Plug Control Module or PCM
Common Causes of P0383 OBD II Trouble Code
Start with checking for a fully charged battery
Check the wiring for defects
Using a voltmeter, check for battery voltage to the glow plug relay main supply terminal. Have a helper turn the key on and check the opposite terminal for voltage drop. If there is a drop over a half-volt replace the relay.
Check for power from the ignition switch to the relay with the key on
Check for relay actuation by disconnecting the oil temperature sensor and turning on the key. It will click when activated. Remove the ground on the small relay terminal and jumper it to ground. If it works now there is a problem with the module or PCM
Check the glow plugs for an open circuit. Pull the connector off the glow plugs. Use a test light and connect it to the positive battery terminal. Touch each terminal to a glow plug. Each should show a good ground. They can also be tested with an ohmmeter. Each should have less than .4-ohms, or very low resistance.
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