P0683 PCM Glow Plug Control Module Communication Circuit Code

OBD-II Trouble Code - P0683 - Data Sheet

Glow plug control module to PCM communication circuit.

Code P0683 indicates that the diesel engine has a problem with the glow plug module communication module, which was detected by the transmission control module or another control module associated with the PCM.

What does trouble code P0683 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code. It is considered universal as it applies to all makes and models of vehicles (1996 and newer), although the specific repair steps may differ slightly depending on the model.

The P0683 code indicates that communication has been lost between the glow plug control module and the PCM communication circuit. An error has occurred that prevents the powertrain control module (PCM) from transmitting commands to the glow plug control module. The command is essentially an on and off signal.

The codes do not indicate a specific part of the system, but only the area of ​​failure. Glow plug circuitry is relatively simple and can be diagnosed and repaired with little automotive knowledge other than basic knowledge of using a volt / ohmmeter.

What are glow plugs for?

Understanding their function requires a basic understanding of how a diesel engine works.

Unlike a gasoline engine, which needs a spark to ignite the fuel, a diesel engine uses an extremely high compression ratio. Highly compressed air gets very hot. Diesel compresses the air in its cylinders to such an extent that the air reaches a temperature sufficient for the fuel to self-ignite.

When the diesel engine block is cold, it is difficult to generate enough compression heat to ignite the fuel. This is because a cold engine block cools the air, causing the temperature to rise slowly enough to start.

When the vehicle's powertrain control module (PCM) detects a cold engine from the transmission oil and transmission temperature sensors, it turns on the glow plugs. The glow plugs glow red hot and transfer heat to the combustion chamber, helping to start the engine. They run on a timer and only run for a few seconds. A little more, and they will quickly burn out.

How do they work?

When the PCM detects that the engine is cold, it grounds the glow plug control module (GPCM). Once grounded, the GPCM grounds the glow plug solenoid (same as the starter solenoid) at the valve cover.

The solenoid, in turn, transfers power to the glow plug bus. The bus has a separate wire for each glow plug. Power is sent to the glow plugs, where they heat the cylinder to aid starting.

GPCM is a timer that only activates for a few seconds. This is enough to start the engine, but at the same time it protects the glow plugs from overheating during prolonged use.

Symptoms

Symptoms of a P0683 code may include:

• The check engine light will illuminate and the above codes will be set.
• If one or two glow plugs are out of order, then the indication will be negligible. If the engine is very cold, starting can be a little more difficult.
• The engine may fail until it has warmed up enough.
• If more than two glow plugs are faulty, the engine will be very difficult to start.

Possible Causes of Code P0683

Reasons for this DTC may include:

• Open or short circuit in the wiring from the PCM to the GPCM, to the bus, or from the bus to the glow plug.
• Defective glow plug
• Loose or corroded joints
• Unsuccessful GPCM
• Loose or corroded connections on the glow plug solenoid.
• Glow plug solenoid malfunction
• Insufficient battery charge on solenoid
• The P0670 code may accompany this code. This code indicates a problem with the harness from the GPCM to the solenoid.

Diagnostic and repair stages

Over the years, I've found this to be a common problem with diesels regardless of manufacturer. Because of the high amperage required to operate glow plugs and their tendency to burn out, I suggest starting with the most common problems.

The GPCM uses low amperage and, although possible, is the least likely to fail. The solenoid is also rarely replaced. When you are dealing with high amperage, even the slightest loosening of the connection will create an arc and burn the connector.

• Inspect the wiring from PCM to GPCM. Continue down to the solenoid on the valve cover, from the solenoid to the bus and down to the glow plugs. Look for loose or corroded connectors.
• Disconnect the black and green electrical connectors from the GPCM. Inspect the connector for extruded pins and corrosion.
• Use an ohmmeter to test each terminal for a short to ground. Repair the short circuit if necessary.
• Apply dielectric grease to the pins and reconnect the harness to the GPCM.
• Inspect the positive battery and the GPCM connection on the glow plug solenoid. Make sure all wires are clean and secure.
• Inspect the glow plug tire. Check the connection of each wire on the bus and make sure it is clean and tight.
• Remove the wire from the glow plug and check for a short to ground.
• Using an ohmmeter, examine the glow plug terminal with one wire and ground the other. The glow plug is out of order if the resistance is not between 0.5 and 2.0 ohms.
• Check the resistance in the wiring from the glow plug to the busbar. Resistance should also be in the range of 0.5 to 2.0. If not, replace the wire.

If the above does not help identify the problem, obtain your service manual and go to the page for the glow plug schematic. Look at the color and pin number for the GPCM power and power supply on the solenoid. Check these terminals according to the voltmeter directions.

If there is no power to the GPCM, the PCM is faulty. If there is voltage across the GPCM, check the voltage from the GPCM to the solenoid. If there is no voltage to the solenoid, replace the GPCM.

HOW DOES A MECHANIC DIAGNOSTIC CODE P0683?

A P0683 diagnosis should start with CAN, and may require Tech II or Authohex for faster, more accurate diagnosis in this complex tangle of wires and harnesses. The memory in the PCM must be retained until the need for reprogramming after repair is eliminated.

Using a CAN scanner will show the mechanics of the pin values ​​and how the control modules work without endangering individual blocks. The scanner will look for problems in the circuit that occur while the vehicle is moving. Individual testing of each circuit is not possible, as thousands must be tested, and one module can be destroyed if not tested properly.

The mechanic should also check for intermittent or intermittent system events, and make sure all transmission or engine cables or wires are secure. All control module circuits should be tested for continuity to battery ground. The mechanic will visually inspect the electrical connections, in particular, looking for corrosion or loose connections that increase the resistance of the circuit, causing the code to be stored.

It is helpful to refer to the vehicle CAN bus system wiring diagram or pin value table, check continuity between each controller terminal with a digital ohmmeter, and repair short or open circuits as necessary.

COMMON ERRORS WHEN DIAGNOSING CODE P0683

Always diagnose codes in the order in which they were stored to avoid failed repairs. The freeze frame data indicates the order in which the codes were stored and only after the previous codes have been processed can you proceed with code P0683.

HOW SERIOUS CODE P0683 IS?

Code P0683 is one that has a lot of room for misdiagnosis because everything from fuel injector codes and transmission codes to engine misfiring and just about any other drivability code can be accompanied by this communication code. Proper diagnosis is important to address the underlying cause.

WHAT REPAIRS CAN FIX CODE P0683?

The most common repair code for P0683 is:

• However, checking the code with a scanner and a digital volt/ohmmeter may require an Autohex or Tech II for a lot of wiring to verify this repair. The CAN scanner is really the perfect solution.
• Check all wiring and connectors and replace or repair any parts that are corroded, damaged, shorted, open, or disconnected, including fuses and components. After each repair, a new check is required.
• When rescanning, check the control module ground circuits and check the continuity of the battery ground circuit, and check for an open or faulty system ground.
• Examine the CAN bus system diagram, fix the value diagram and check the controller connections. What are the values ​​from the manufacturer? Compare and then repair all chains.

ADDITIONAL COMMENTS REGARDING CODE P0683 CONSIDERATION

Replace broken wiring instead of handling them individually in wire harnesses.

Tata Manza quadrajet p0683 glow plug controller circuit open code fixed

Need more help with your p0683 code?

If you still need help with DTC P0683, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.