P1291 code possible causes
- Air heater relay fault
- Battery cable condition
- Electrical circuit fault
How is P1291 code repair performed?
Start by checking the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
What are the possible symptoms of P1291 code?
- Check engine light on (or Service Engine Soon warning light)
What does P1291 code mean?
Intake air heater temperature rise is monitored during the first 15 seconds of engine operation. P1291 code may be stored if the initial reading of the intake air temperature (IAT) sensor is 0 to 66°F (-17.8 to 18.8°C), the battery temperature sensor (BTS) and the intake air temperature (IAT) sensor are within 10°F of each other, the time between the end of preheating and engine running status is less than 30 seconds, the engine is cranked for less than 5 seconds before engine start, preheating is completed before engine start, post-heating is active, and no IAT sensor or intake air heater relay DTCs exist.