What does it mean?
P1557 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 7 Injector Circuit Range/Performance .
Symptoms
- Check engine light on, usually accompanied by a cylinder 7 misfire code
- Persistent misfire and an uneven idle that shakes the vehicle
- Poor throttle response and reduced power on one bank
- Extended cranking, or a start that catches and then stumbles
- Increased fuel consumption and an unburnt fuel odour
- On some vehicles the module cuts fuel to that cylinder, giving a clear power loss
Likely causes
- Injector winding resistance out of tolerance, typically from heat ageing on one bank of a V engine
- Corroded or oil-filled connector at the cylinder 7 injector
- Chafed injector wiring against the intake manifold or a fuel rail bracket
- High resistance crimp or a broken strand inside the injector sub-harness
- Blocked, stuck or leaking injector that alters the measured circuit response
- Injector coding not carried over after the part was replaced on a common rail engine
- Damaged output driver for that channel inside the PCM
How to fix it
- Save the freeze frame and check misfire counts and injector balance for cylinder 7
- Verify that the PCM is pulsing the injector with a test light or a scope on the connector
- Measure and compare injector resistance across the whole bank, not just the flagged cylinder
- Relocate the injector to another cylinder to confirm whether the fault is in the part or the circuit
- Inspect the sub-harness under the intake manifold for chafing and heat damage
- Replace or service the injector and enter the calibration code where required
- Repair wiring faults, clear the code and confirm balanced fuel trims and smooth running on a road test