P0657 code definition
When the PCM or one of the control modules that support and feed into it (e.g., the fuel control module, antilock brake control module, body control module, etc.) detects a fault in the supply voltage to the “A” circuit, the P0657 code will be stored, and the Check Engine light will be illuminated.
What the P0657 code means
The PCM and the vehicles other control modules are constantly performing self-checks and self-monitoring to ensure that the PCM is functioning efficiently and properly. The PCM does this through checks of output signals, internal circuits, and checks on its internal memory status. If there’s a malfunction during this monitoring process, the PCM will store the P0657 code after a predetermined number of drive cycles. Some vehicles will require up to eight cycles of malfunctions, while others will require fewer.
What causes the P0657 code?
The most common causes of a P0657 code include:
- An open or shorted circuit in the PCM
- An open or shorted circuit between two interfacing supporting control modules
- An open or shorted circuit between the engine sensors and the PCM
- A disconnected ground wire running to a control module
- An internal malfunction within the PCM
What are the symptoms of the P0657 code?
When a P0657 code is stored, you can expect the following symptoms:
- The Check Engine light will illuminate.
- The engine may be difficult to start or may not start at all.
- The engine may run rough at idle or while driving at speed.
- The engine may misfire and/or have a lack of power, especially when accelerating.
How does a mechanic diagnose the P0657 code?
When diagnosing a P0657 code, a mechanic will first use an OBD-II scanner to identify the code and any other codes that may be related to it. They will then perform a visual inspection of any affected circuits to look for damaged, corroded, or loose wires or connectors.
If they do not see any damage to the circuit(s), they will likely use an ohmmeter to test the circuit(s) for shorts or open connections. Once they find the cause of the problem, they’ll diagnose and fix it, and then they’ll retest the system to ensure that the code is not stored again.
Common mistakes when diagnosing the P0657 code
When a P0657 code is stored, other codes may also be stored and symptoms may occur as a result of the breakdown in internal communication due to the open or shorted circuit. Resolving these symptoms will not solve the underlying problem, which is the open or shorted circuit. So, if other codes are found in relation to a P0657 code, you will almost always want to deal with the P0657 code first.
How serious is the P0657 code?
Though it may not have severe symptoms of its own, a P0657 code can cause other problems in the engine due to a malfunction within the PCM or one of its circuits. In addition to a rough riding engine, this can lead to a number of other potentially severe and dangerous problems. Thus, it’s important to get your P0657 code diagnosed and resolved ASAP.
What repairs can fix the P0657 code?
Though the problem causing this code will almost always be a shorted or open circuit, there are a few different repairs that may fix it, including:
- Securing and tightening PCM connectors and/or ground wires.
- Repairing or replacing the PCM wiring harness.
- Reprogramming the PCM.
- Replacing the PCM.
Additional comments for consideration regarding the P0657 code
Even if your vehicle seems to be running smoothly with a stored P0657 code, if you need to get an OBD-II emissions test performed in order to renew your registration, you will need to address the problem and clear the code. If the code is stored at the time of your emissions test, it will illuminate the Check Engine light, which will make your vehicle ineligible to pass.
Need help with a P0657 code?
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