Fault code: 8705 SCANIA

Error identification:

The voltage in the circuit has been below the permitted level.

Cause:

Possible causes:

• Open circuit in the charge air pressure sensor circuit.

• Fault in the circuit of the coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor or fan speed sensor.

Notes:

There is a common voltage supply for the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor or fan speed sensor. If a fault occurs in one of the sensors, the other sensor circuits may be affected.

If the voltage is outside the permitted range, the control unit uses a pre-programmed value.

An active fault code limits the maximum engine torque by approximately 40%. The engine also responds more slowly than normal to throttle actuation. This is because the smoke limiter is not operating correctly.

For engines with EGR, the engine runs with EGR but without any feedback from the mass flow sensor. This means that the control unit only makes a rough adjustment of EGR content using predefined values for the position of the EGR damper. Calibration of the mass flow sensor is switched off.

The fault affects the vehicle s emissions of nitrogen oxides (NOx) and the lamp which warns about a high level of contaminants comes on in the instrument cluster. A text message is also displayed in vehicles with NOx monitoring.

Vehicles with NOx monitoring

An active fault code cannot be cleared from the control unit. When the fault has been rectified, the control unit must verify that the fault has been rectified in order for the fault code to become inactive.

Action:

Check the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor and fan speed sensor, along with the harness-to-harness connectors and electrical cables in the circuits.

Check that the intake system is not blocked by for example ice or debris.

Also check that the air bellows are free of faults and are not squeezed together.

To verify that the fault has been rectified:

Start the engine and run it at idling speed for at least 15 seconds.

If the fault is resolved, the fault code becomes inactive. If this is the case, clear the fault code.

Switch the power off and on with the starter key three times in succession at 10 second intervals to turn off the warning lamp.

Error identification:

The signal from the NOx sensor does not change as expected.

Cause:

The NOx sensor is defective or positioned incorrectly.

Notes:

–

Action:

Check that the NOx sensor is correctly positioned and if so renew the NOx sensor.

Verification

There are two alternatives:

• Run Verifying rectified fault codes for NOx monitoring. The test should be carried out outdoors because the exhaust gases become very hot and there is a risk that the vehicle exhaust extraction system will be damaged. The test takes approximately 5-30 minutes to carry out, depending on which fault codes are active.

• Road test the vehicle and check that the engine and catalytic converter are warmed up. The NOx sensor is activated when the temperature exceeds 120°C. The verification test will start 5 minutes after the NOx sensor has been activated.

If the fault is resolved, the fault code becomes inactive. Clear the fault code.