PACCAR MX (2004 Emissions) Fault Code: P170B Lambda – Data Valid but Too High, Most Severe

PACCAR MX (2004 Emissions) Fault Code: P170B Lambda – Data Valid but Too High, Most Severe

SET CONDITIONS:
The PCI ECU (D420) detects that the air/fuel ratio is too high for more than 40 seconds.

DIAGNOSTIC CONDITION:
This diagnostic runs:
1. When the engine speed is between 950 and 2000 rpm and
2. When the engine is running at a steady load and
3. When the coolant temperature is above 50°C [122°F] and
4. The engine mode is SCR high efficiency or standard or protection
5. The lambda sensor (F834) is in the operating mode (if applicable)

CORRESPONDING OBD READINESS MONITOR:
Exhaust gas sensors monitor

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 following conditions:
– Corresponding readiness monitor displays ‘Ready’
– Diagnostic conditions are met
– Set conditions are met
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Leaking exhaust system
2. Faulty fuel system
3. Lambda sensor deviation (if equipped with lambda sensor)
4. NOx sensor before catalyst deviation (only if NOT equipped with lambda sensor)

ADDITIONAL INFORMATION:
IMPORTANT: Depending on the production date of the vehicle, either the lambda sensor (F834) or the NOx sensor before catalyst (F844) is used to determine the oxygen concentration in the exhaust gas.

Typically, high value air/fuel ratio indicates high oxygen concentration in the exhaust system.