What does it mean?
P1607 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: PCM Internal Circuit 'A' Malfunction .
Symptoms
- MIL (check engine lamp) on, with the code returning quickly after each clear
- Several unrelated codes stored at once, some of them implausible
- Reduced power and limp mode
- Intermittent stalling, hard starting or an occasional no-start
- Scan tool communication dropping in and out
- Functions controlled through that circuit group behaving erratically
Likely causes
- Low, unstable or spiking supply voltage, often after jump starting or with a failing regulator
- Corroded or high-resistance module grounds
- Moisture inside the module connector or the module case
- An external circuit in that group shorted to ground or to battery positive, loading the internal stage
- Programming interrupted or an incorrect calibration loaded
- Heat and vibration damage to internal solder joints over years of service
- Aftermarket wiring, alarm or tuning hardware spliced into the module harness
How to fix it
- Record all codes and freeze frame data, then clear and see which ones return first
- Test the battery and charging system and correct any voltage problem before going further
- Voltage-drop test each module ground and confirm the supply at the module connector
- Inspect the connector and module case for water, corrosion and previously repaired wiring
- Disconnect the actuators fed by the suspect circuit group one at a time to find an external short
- Verify the calibration is correct for the vehicle and reflash with a stable power supply connected
- Replace and program the PCM only after supply, ground and external circuits are proven good