P1291

Tests 1 - 2:

Tests 3 - 8:

Tests 9 - 14:

Tests 15 - 17:

SYMPTOM
P1291 - NO TEMPERATURE RISE SEEN FROM INTAKE AIR HEATERS

WHEN MONITORED
First 15 seconds of engine operation.

SET CONDITION
Initial IAT between 0 °F & 66 °F, battery temperature & IAT within 10 °F of each other, time between end of preheat & engine run state is < 30 seconds, engine cranked < 5 seconds before start, preheat completed before start, post-heat active, no IAT/IAH relay DTC's.

POSSIBLE CAUSES
- DTC not equal to freeze frame DTC
- DTC specific good trips not change to zero
- Inactive trouble code condition
- # 1 intake air heater
- # 2 intake air heater
- # 1 intake air heater relay
- # 2 intake air heater relay
- Battery cable from # 1 relay to # 1 heater
- Battery cable from # 2 relay to # 2 heater
- Battery cable from battery to heater relay # 1
- Battery cable from battery to heater relay # 2