P0383 DTC Glow Plug Control Module Circuit Low

Description and meaning of DTC p0383

The OBD (on board diagnostics) code P0383 is generic and encompasses all brands of late model diesel engines, including those diesels found in Ford, Dodge, Chevrolet, GMC, and VW Volkswagen vehicles. To understand the significance of this code, its ramifications and symptoms, it is important to understand the dynamics at work. Unlike a conventional gas engine, a diesel doesn't rely on a compressed fuel mixture and an electrical source of ignition to operate. Diesels have much higher compression than gas engines. This high compression causes the air in the cylinder to reach over 600 degrees - sufficient to ignite the diesel fuel. When the piston reaches top dead center of the cylinder, high-pressure fuel sprays into the cylinder. It immediately ignites when it encounters the super-heated air and the expanding gases drive the piston down. Glow PlugSince the diesel engine requires super-heated air to ignite the fuel, a problem arises when the engine is cold. When starting a cold engine, it is difficult to super-heat the air when its heat is quickly lost to the cold cylinder head. The glow plug is the solution. Installed in the cylinder head, the pencil shaped plug heats up until it glows for up to ten seconds. This results in the surrounding cylinder wall temperature to rise allowing the heat of compression to rise sufficiently for ignition.

p0383 diagnostic trouble code symptoms

The glow plug warning light will illuminate and the engine will be slow to start in warm weather, or fail to start in cold weather. If the engine does start there will be a pronounced knocking noise until the engine warms up to operating temperature. White smoke will be visible from the exhaust as the excess fuel from the hard start burns off. The engine will have a noticeable miss until the cylinder head temperatures rise sufficiently to support complete combustion.

DTC p0383 - possible causes

They have a life expectancy of 30,000 - 40,000 miles and have reached their useful life and need replacement. Poor injection timing will cause undue wear on the glow plug. Next to the time replacement, a stuck glow plug relay or timer module will burn them out faster than a flea can jump on a slow moving dog.

How to fix OBD-II diagnostic trouble code p0383

Start with checking for a fully charged batteryCheck the wiring for defectsUsing 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 onCheck 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 PCMCheck 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. Other Glow Plug related DTCs: P0380, P0381, P0382, P0383, P0384, P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678, P0679, P0680, P0681, P0682, P0683, P0684.

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