P0654 code definition
The P0654 code is stored when the PCM detects a voltage reading from the engine RPM output circuit that does not align with the acceptable range as determined by the manufacturer’s specifications.
What the P0654 code means
During operation, the engine speed is monitored by the PCM through several components. One of these is the Engine RPM Output Circuit, which creates a signal through a grounding process that involves a driver (an internal switch). Each driver is monitored by the PCM through a fault line, sending voltage readings to the PCM for comparison to the manufacturer’s specifications. If the voltage is too high or too low compared to what it is supposed to be in the current operation conditions, the PCM will store the P0654 code.
What causes the P0654 code?
The most common cause behind the P0654 code is a defect in the system circuitry, such as loose or corroded wiring, or loose or broken electrical connectors.
Other causes may include:
- A faulty instrument cluster
- An open or shorted instrument cluster harness
- A faulty tachometer
- A bad crankshaft or camshaft sensor
- A faulty PCM, in rare cases
What are the symptoms of the P0654 code?
Most of the time, the illuminated Check Engine light will be the only symptom that the vehicle owner will observe; however, an inoperative or erratic tachometer, and possibly a no start condition, can also occur.
How does a mechanic diagnose the P0654 code?
In order to diagnose the P0654 code, the mechanic should begin by verifying the code with an OBD-II scanner. Once the code has been verified, they should perform a visual inspection of all electrical components, such as wiring and connectors. Because faulty electrical components are the most likely cause of this code, a thorough examination is required. After ensuring that any loose, corroded, or broken components are repaired, the code should be cleared from the PCM and the system should be retested.
If the code comes back after this repair, then the mechanic has diagnosed a more complex issue within the engine RPM output circuit or related components. A specialized scanner, such as an Autohex, may be required to pinpoint the exact area causing the problem. The mechanic should continue checking each component for voltage readings, comparing those to the manufacturer’s specifications, until they’ve discovered the component or sensor that is not operating correctly.
Common mistakes when diagnosing the P0654 code
Most often, mechanics report that a faulty tachometer is blamed, when the PCM driver was actually at fault.
How serious is the P0654 code?
If the P0654 code is detected, it represents an issue that should be addressed right away. This code means that the engine speed cannot be correctly monitored, which could eventually lead to larger issues or dangerous driving conditions.
What repairs can fix the P0654 code?
In order to fix the P0654 code, a technician may attempt several types of repairs. These include:
- Repair any defects in the system circuitry, replacing loose, corroded, or broken electrical components as necessary.
- Replace a faulty instrument cluster.
- Repair an open or shorted instrument cluster harness.
- Replace a faulty tachometer.
- Replace a bad crankshaft or camshaft sensor.
- Replace a faulty PCM, in rare cases.
Additional comments for consideration regarding the P0654 code
If the issue is found to be a bad crankshaft or camshaft sensor, and the part must be replaced, most manufacturers recommended replacing both simultaneously. These sensors work best when they wear at the same time.
Need help with a P0654 code?
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