P0655 code definition
A P0655 code means that the powertrain control module (PCM) has detected that there is an abnormal voltage reading coming from the engine hot lamp output circuit.
What the P0655 code means
The P0655 is an OBD-II generic code which indicates that the circuitry meant to relay a pending engine overheat is experiencing a voltage-related malfunction. Typically, it means that there is a problem in the circuitry that operates this system.
What causes the P0655 code?
A P0655 is caused by one of the following:
- Defective circuitry in the system, possibly due to corroded, broken or loose wiring or connections between the PCM and the sensor.
- Defective PCM
- An engine over temp indicator bulb malfunction
- Engine temperature sensor defect
What are the symptoms of the P0655 code?
The P0655 code has few symptoms and will often only store the code. However, it may trigger a check engine light or a flashing engine temperature indicator.
How does a mechanic diagnose the P0655 code?
The P0655 is diagnosed with an OBD-II scanner, and it is important to pay attention to other codes relating to engine temperature that may have been stored before the P0655. Freeze frame data is important to proper diagnosis, and resetting, road testing and retesting the vehicle is the next step. If the code returns, visually inspect the wiring and connections, replacing or repairing any components, fuses, wiring and connectors where needed. Retest the system and use the freeze frame data and codes to identify the issue.
It is highly recommended to use a manufacturer's suggested testing method when forced to diagnose individual control models. Replacing only as required, and reprogramming the PCM. It may be necessary to use an Autohex or Tech II scanner because of the complexity of the electrical system testing and then repair any open or shorted circuits as needed.
Common mistakes when diagnosing the P0655 code
Diagnostic errors tend to occur when a mechanic does not compare their findings against a manufacturer's reference values. Additionally, it is important to perform a close visual exam to find any loose connectors that cause such codes as the P0655 to be stored. A common misdiagnosis is to replace the engine coolant temperature sensor though it is the PCM driver that is causing the problem.
How serious is the P0655 code?
The P0655 code will not prevent the car from starting, but it can be that the vehicle has a faulty sensor that could easily lead to an overheating issue.
What repairs can fix the P0655 code?
The most common repairs used for P0655 are:
- Checking the code with a scanner, resetting and doing a road test to see if the P0655 code returns.
- Visually inspecting all electrical connections, the PCM and the engine wiring harness. Any damaged, disconnected or corroded components, wires, or connectors will be repaired and reinstalled.
- Though individual control modules rarely fail, they will be tested according to manufacturer's specs and replaced if needed. The PCM is then reprogrammed.
Additional comments for consideration regarding the P0655 code
The PCM needs accurate data from the engine in order to control many other areas of the vehicle. This is why this code must be diagnosed starting with the PCM and the engine wiring harnesses, grounds straps or wires and all electrical connections. The CAN bus network is also a huge part of this repair, but you should not attempt to manually check the wires as a probe can cause multiple controller failures if used improperly.
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