PACCAR MX (2004 Emissions) Fault Code: P1235 Turbo Speed – Data Erratic, Intermittent, or Incorrect

Description

SET CONDITIONS:
The PCI ECU (D420) detects that the measured turbo speed differs too much from the expected turbo speed for more than 120 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine is running at a steady load and the coolant temperature is above 50?C [122?F].

CORRESPONDING OBD READINESS MONITOR:
None

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

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Fault on turbo speed sensor
2. Fault on boost pressure sensor

ADDITIONAL INFORMATION:
1. The turbo speed is measured by the turbo speed sensor (F683).
2. The boost pressure sensor signal is used to calculate the expected turbo speed.