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Technical Description of OBD-II Trouble Code
Malfunction in the Engine Hot Lamp Output Control Circuit
What does that signify?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Alfa Romeo, Peugeot, MG, Dodge, Buick, Cadillac, Chevrolet, Ford, GMC, Opel, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P0655 indicates that the powertrain control module (PCM), or one of the related controllers, has detected an inconsistency in the engine hot lamp output control circuit.
The engine hot lamp is designed to visually warn the driver when the engine is overheating. It is an integral part of the instrument panel. The PCM receives a signal from the engine coolant temperature sensor, allowing it to monitor the engine coolant temperature whenever the engine is running or the ignition switch is in the ON position. This data is primarily used for calculating engine fuel delivery and ignition timing strategy, and is then output to the engine hot lamp and/or instrument panel controller. It may also be output to other controllers. For example, the engine hot lamp control circuit may be output to the climate control module to disable the air conditioning compressor if the engine overheats.
If a problem is detected in monitoring the engine hot lamp output control circuit, a code P0655 will be stored and a malfunction indicator lamp (MIL) may illuminate.
Typical simple gauges:
What is the severity of this DTC?
A P0655 should be considered severe because it can result in various drivability issues and fail to warn the driver in the event of engine overheating.
What are some of the symptoms of the code?
Symptoms of a P0655 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0655 troubleshooting steps?
If there are engine overtemp codes or engine temperature sensor codes present, diagnose and repair those issues before attempting to diagnose a stored P0655 code.
Ensure that the engine is filled with the appropriate coolant and is not overheating.
Refer to your vehicle information source for technical service bulletins (TSB) that match the stored code, vehicle (year, make, model, and engine), and exhibited symptoms. If you find the relevant TSB, it may provide helpful diagnostic information.
To accurately diagnose a code P0655, you will need a diagnostic scanner and a digital volt/ohmmeter. You will also require a reliable source of vehicle information.
Start by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. It is advisable to write down this information in case the code proves to be intermittent.
After recording all relevant information, clear the codes and, if possible, test drive the vehicle until the code is reset or the PCM enters readiness mode.
If the PCM enters readiness mode, the code is intermittent and will be even more challenging to diagnose. The condition that caused the P0655 code to be stored may need to worsen before an accurate diagnosis can be made. On the other hand, if the code fails to reset and there are no drivability symptoms, the vehicle can be operated normally.
If the P0655 code is immediately reset, proceed with a visual inspection of the system’s related wiring and connectors. Repair or replace any broken or unplugged harnesses as necessary.
If the wiring and connectors appear to be functional, use your source of vehicle information to obtain the appropriate wiring diagrams, connector face views, connector pin-out charts, and diagnostic flow charts.
Once you have the correct information, use your DVOM to test the engine hot lamp output circuit at the appropriate pin of the PCM connector. If no engine hot lamp output signal is detected, suspect that the PCM is defective or there is a PCM programming error.
If an engine hot lamp output signal is detected at the PCM connector, test the corresponding circuit (as presented) at the engine hot lamp pin of the instrument panel connector. If the engine hot lamp signal is not detected, there is an open circuit between the PCM and the hot lamp in the instrument panel. Repair or replace the circuit and retest.
Professional Service
While we always recommend resolving this issue through mechanical means, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to function. If you are interested in this option, please upload your ECU file to our portal.
