What does it mean?
P1237 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 1 Fuel Injection Circuit Open Circuit .
Symptoms
- Hard misfire on cylinder 1, with the check engine lamp often flashing
- Very rough idle, heavy vibration and a noticeable loss of power
- Unburnt fuel and air passing to the exhaust, which can overheat the catalytic converter
- Engine runs on the remaining cylinders and will barely pull away
- Fuel consumption rises and the exhaust note becomes uneven
Likely causes
- Broken injector wire, most often where the loom flexes near the cylinder head
- Injector connector unplugged, not fully latched, or with a terminal pushed out of the housing
- Open injector winding after an internal failure
- Corroded terminals that have lost contact pressure
- Blown fuse or open supply feed serving that injector
- Broken solder joint or an open driver inside the module
How to fix it
- Read the codes and note whether other injectors report open at the same time, which points to a shared feed
- Check the injector fuse and the supply voltage at the connector with the ignition on
- Unplug the connector and inspect for a pushed-out terminal, corrosion and a broken lock
- Measure the injector winding resistance; an infinite reading confirms an open injector
- Check continuity of the control wire from the injector connector to the module
- Use a test light or a noid tool to see whether the module is pulsing the circuit
- Repair the wiring or replace the injector as the test results dictate, then confirm the misfire counter stays at zero
- Evaluate the module driver last if supply, wiring and injector are all good