2013 PACCAR MX-13 – P0135 Lambda sensor heater – Current too low or open circuit on ECU D420 pin C46

Fault code information

1 trip MIL
3 drive cycle recovery
Readiness group – None
Freeze frame type –Exhaust gas

Description of component(s)

The lambda sensor measures the oxygen concentration in the exhaust gases after the BPV valve.

Air/fuel ratio
The PCI ECU uses the measured oxygen concentration in the exhaust to determine the aratio of the combustion process.
Typical air/fuel ratios are 18 to 45. A high value indicates a high oxygen concentration measured by the lambda sensor.

Sensor heater
The sensor has an integrated heater to maintain a sensor operating temperature of approximately 750°C [1382°F]. The PCI ECU controls the heater.
* The first stage starts when the ignition is keyed on. The sensor is heated to a value at which any                    condensate evaporates from the sensor.
* The second stage starts after the ‘dew point’ is reached. The sensor is heated to its operating                         temperature of approximately 750°C [1382°F]. The PCI ECU determines the ‘dew point’ by                           calculating how much energy (heat by burning fuel in the engine) is pumped through the exhaust. If           the ‘dew point’ is not/no longer reached, the sensor temperature stays at/drops to the standby                     temperature, similar to the first stage heating.

Effect on the system
* Determines the air/fuel ratio of the combustion process
* Controls the smoke limit; where the measured exhaust gas oxygen concentration is compared with a        target value for smoke limitation. A higher measured oxygen concentration results in lower                            calculated soot formation by the engine.
* Controls NOx emissions; determines whether the target Exhaust Gas Recirculation is being achieved     to control NOx emissions. A higher measured oxygen concentration results in higher calculated NOx       formation by the engine.
* Controls regeneration of the diesel particulate filter (DPF). The soot particles in the DPF are ‘burned’     using the oxygen present in the exhaust gas

Location of component(s)

Diagnostic condition

This diagnostic starts five minutes after the engine starts.

Set condition of fault code

This diagnostic starts five minutes after the engine starts. The diagnostic runs continuously.

Reset condition of fault code

This fault code will change to inactive immediately after the diagnostic runs and passes.

Electrical diagram(s)

Technical data

Possible causes

* Faulty wiring
* Faulty connector
* Faulty sensor

Additional information

No additional information available.

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