PACCAR MX (2004 Emissions) Fault Code: P009A Ambient Temperature – Data Erratic, Intermittent, or Incorrect

PACCAR MX (2004 Emissions) Fault Code: P009A Ambient Temperature – Data Erratic, Intermittent, or Incorrect

SET CONDITIONS:
The PCI ECU (D420) detects that the measured ambient temperature differs too much from the calculated ambient temperature for more than 300 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. 300 seconds after an engine start and
2. When the engine is running at a steady load and
3. Vehicle speed is above 35 km/h [22 mph]

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

POSSIBLE CAUSES:
1. Ambient temperature sensor deviation
2. Humidity sensor deviation

ADDITIONAL INFORMATION:
1. The measured ambient temperature is compared with the calculated ambient temperature.

2. The ambient temperature is calculated by the PCI ECU. Other involved sensors and input signals used to calculate the ambient temperature are the precompressor temperature (humidity sensor (F852)), engine cooling fan state (on or off), vehicle speed, and fuel injection quantity.