What does it mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Alfa Romeo, Peugeot, MG, Dodge, Buick, Cadillac, Chevrolet, Ford, GMC, Opel, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
A stored P0655 code means that the powertrain control module (PCM), or one of the other associated controllers, has detected an anomaly in the engine hot lamp output control circuit.
The engine hot lamp is designed to provide the driver with a visual warning light when the engine overheats. The engine hot lamp is an integral part of the dashboard. The PCM receives a signal from the engine coolant temperature sensor. This signal allows the PCM 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 distribution and ignition timing strategy, and is then transmitted to the engine hot lamp and/or the dashboard controller. It may also be sent to other controllers. For example, the engine hot lamp control circuit can be sent to the climate control module so that the air conditioning compressor can be deactivated in case of engine overheating.
If a problem is detected while monitoring the engine hot lamp output control circuit, a P0655 code will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Typical simple gauges:
P0655 Simple Gauges
How severe is this DTC?
A P0655 should be classified as severe because it could lead to many driving issues and not warn the driver in case of engine overheating.
What are some of the symptoms of the code?
Symptoms of a P0655 trouble code may include:
Engine driving problems
Inoperative engine hot lamp
Engine hot lamp constantly illuminated
What are some common causes of the code?
Causes
of this code may include:
Open or shorted circuit between the PCM and the dashboard or other controllers
PCM programming error
Faulty controller or PCM
What are the troubleshooting steps for P0655?
If there are engine overheating codes or engine temperature sensor codes; diagnose and repair those before attempting to diagnose a stored P0655.
Ensure the engine is filled with appropriate coolant and is not overheating.
Consult your vehicle’s information source for technical service bulletins (TSBs) that reproduce the stored code, the vehicle (year, make, model, and engine), and the presented symptoms. If you find the appropriate TSB, it may provide useful diagnostic information.
A diagnostic scanner and a digital volt/ohmmeter will be needed to accurately diagnose a P0655 code. A reliable source of vehicle information will also be required.
Start by connecting the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You’ll want to note this information, just in case the code proves to be intermittent.
After recording all relevant information, clear the codes and test the vehicle (if possible) 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 difficult to diagnose. The condition that caused the P0655 to be stored may need to worsen before an accurate diagnosis can be reached. On the other hand, if the code does not reset and no driving symptoms manifest, the vehicle may be operating normally.
If the P0655 is immediately reset, proceed with a visual inspection of the wiring and connectors related to the system. Harnesses that have been broken or disconnected should be repaired or replaced as needed.
If the wiring and connectors appear functional, use your vehicle information source to obtain the appropriate wiring diagrams, connector face views, connector pinout diagrams, and diagnostic flowcharts.
Once you have the correct information, use your DVOM to test the engine output circuit at the appropriate PCM connector pin. If no engine hot lamp output signal is found, suspect that the PCM is faulty or there is a PCM programming error.
If an engine hot lamp output signal is found at the PCM connector, test the corresponding circuit (as presented) at the engine hot lamp pin of the dashboard connector. If the engine hot lamp signal is not found, you have an open circuit between the PCM and the engine hot lamp in the dashboard. Repair or replace the circuit and retest.
If a P0655 code is stored and the engine hot lamp is operational, suspect a faulty PCM or a PCM programming error