DTC Description

If the difference between real and target throttle position is abnormal, the ECM sets DTC P0638.

DTC Detecting Condition

Item

Detecting Condition

Possible Cause

Case 1

DTC

Strategy

Return Spring Check

1.

Throttle stuck

2.

Open in motor circuit

3.

Faulty motor

4.

Faulty ECM

Enable

Conditions

During TPS adaptation

Threshold

Value

Throttle position > Limp-home pos.+3 %

Diagnostic

Time

0.56 sec

MIL ON

Condition

1 driving cycle

Case 2

DTC

Strategy

Abnormal value of TPS re-adaptation

Enable

Conditions

During TPS adaptation (throttle is made to approach the lower mech. throttle limit stop via ramp) Learned value already saved

Threshold

Value

Voltage throttle poti 1 at the lower limit stop < 0.21 V or Voltage throttle poti 2 at the lower limit stop > 4.84 V or Volt. sum throttle poti1 and 2 = 5 V

Diagnostic

Time

0.3 sec

MIL ON

Condition

1 driving cycle

Case 3

DTC

Strategy

Abnormal value of TPS re-adaptation

Enable

Conditions

Delta Limphome(last dcy adaptation - current dcy adaptation) or ETC replaced or ECU reset

Threshold

Value

Voltage throttle poti 1 at the lower limit stop + offset > 0.695 V

Voltage throttle poti 2 at the lower limit stop - offset(0.025 V) < 4.305 V

Diagnostic

Time

0.3 sec

MIL ON

Condition

1 driving cycle

Case 4

DTC

Strategy

TPS re-adapation was failed due to violated input conditions

Enable

Conditions

During TPS adaptation

Threshold

Value

Engine speed > 250 rpm

Vehicle speed > 0 mph

Accel. pedal > 14.9 %

ECT < 5.3 ℃(41.54 °F)

ECT > 100.5 ℃(212.9 °F)

IAT < 5.3 ℃(41.54 °F)

Diagnostic

Time

Immediate

MIL ON

Condition

2 driving cycles

Case 5

DTC Strategy

TPS re-adapation was failed due to violated input conditions

Enable

Conditions

During TPS adaptation

Threshold

Value

Engine speed > 250 rpm

Vehicle speed > 0 mph

Accel. pedal > 14.9 %

ECT < 5.3 ℃(41.54 °F)

ECT > 100.5 ℃(212.9 °F)

IAT < 5.3 ℃(41.54 °F)

Diagnostic

Time

Immediate

MIL ON

Condition

1 driving cycle

Case 6

DTC

Strategy

TPS adaptation fault or abnormal value during the first initialization

Enable

Conditions

First initialization

IG ON

Threshold

Value

Learning stop due to violated input condition and UMA learning error

Diagnostic

Time

Immediate

MIL ON

Condition

1 driving cycle

Case 7

DTC

Strategy

Limp-home check

Enable

Conditions

IG ON

Threshold

Value

Limp-home position < 1.0% or > 19.5%

Diagnostic

Time

Immediate

MIL ON

Condition

2 driving cycles

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