T8 / P0638 00

Read the instructions below then start the fault diagnostic procedure.

Symptom: Fault indicator lamp (for further information see WIS Fault diagnosis, general) Limp home

P0638 00

Fault symptom

Fault indicator lamp (for further information see WIS Fault diagnosis, general)

Limp home

On-board diagnosis

Type of diagnosis:

Continuous

Enable criteria:

Turn Ignition On

Throttle position not requested in rest position (position regulated by Trionic 8).

Fault criteria:

When current throttle position deviates 10% from the requested position.

Dependent:

None

System reaction to a fault:

Correction of mass air flow/combustion for fuel calculation is blocked.

Limited acceleration and idle function.

Cruise control blocked.

Secondary air switched off.

OK report:

Fault criterion not fulfilled and vehicle speed over 0 km/h for more than 60 s.

Fault handling:

Type III

(See section Fault handling III, "Other emission-related components and functions" for more information.)

Checking the wiring harness

Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help

Diagnosis regards:

Electrical fault in connecting leads or component.

Mechanically binding/affected throttle.

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IMPORTANT

•	The DTC can be generated due to faults in connector H42-2 (pins 13, 14, 17, 18, 19 and 20).

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Approximately 3 to 5 seconds after Ignition on and non-actuated accelerator pedal, the throttle resumes rest position to conserve current.

Functions in the diagnostic tool related to the fault:

Test value:

•	Throttle Position Sensor 1

•	Throttle Position Sensor 2

Activation:

•	Throttle Position Test

(See also description of readings/activations in diagnostic tool)