EXPERTEC TSB (416504)

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about .5 at idle to about 4.8 volts at Wide Open throttle (WOT).

The TP sensor is one of the most important inputs to the ECM for fuel control and for many of the ECM control outputs.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 21 will set if:
   • No DTC 33 or DTC 34.
   • Engine is running and RPM greater than 600.
   • TP sensor signal voltage is greater than 3.82 volts.
   • All conditions met for 10 seconds.

     OR

     With throttle closed, the TP sensor should read less than .98 volt. If it doesn't, make sure cruise control and throttle cables are not being held open.

2. With the TP sensor disconnected, the TP sensor voltage should go low, if the ECM and wiring are OK.
3. Probing CKT 470 with a test light checks the 5 volt return circuit. Faulty sensor ground circuit will cause a DTC 21. DTC 33, 66 or 71 may also be set.

DIAGNOSTIC AIDS

A Tech 1 scan tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT.

Also some scan tools will read: throttle angle 0% = closed throttle, 100% = WOT.

An open in CKT 470 will result in a DTC 21.

DTCs 15 and 21 stored at the same time could be the result of an open CKT 470 which would also turn sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from about .5 volt when throttle was closed, to about 4.8 volts when throttle is held at Wide Open Throttle (WOT) position.

Refer to "Intermittents" in "Symptoms," Section "6E3-B".

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about. 5 at idle to about 4.8 volts at Wide Open throttle (WOT).

The TP sensor is one of the most important inputs used by the ECM for fuel control and for many of the ECM control outputs.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 21 will set if:
   • Engine is running and RPM greater than 400.
   • sensor signal voltage is less than about .20 volt for 3 seconds.
2. Simulates DTC 21: (high voltage) If the ECM recognizes the high signal voltage, the ECM and wiring are OK.
3. Check for good sensor connection. If connection is good, replace TP sensor.
4. This simulates a high signal voltage to check for an open in CKT 417.
5. CKT 416 is a 5 volts buffered reference signal. If CKT 416 is shorted to ground, DTC 22 will set. Be sure TP sensor is connected and clear DTC(s) before testing.

DIAGNOSTIC AIDS

A Tech 1 scan tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT.

Also some scan tools will read: throttle angle 0% = closed throttle 100% = WOT.

An open or short to ground in CKTs 416 or 417 will result in a DTC 22.

Scan TP sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from about .5 volt when throttle was closed, to about 4.8 volts when throttle is held at Wide Open Throttle (WOT) position.

Also some scan tools will read throttle angle.

0% = closed throttle.

100% = wide open throttle.

If DTC 22 is set, check CKT 416 for faulty wiring or connections.

It is possible that any of the other sensors sharing the 5V reference line may be causing a DTC 22 to set. Disconnect related sensors and see if DTC 22 resets.

Refer to "Intermittents" in "Symptoms," Section "6E3-B".

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor provides a voltage signal to the PCM that increases as the throttle blade angle increases. This signal voltage will vary from approximately .5 volt at idle to 4.8 volts at Wide Open Throttle (WOT). The TP sensor is one of the most important inputs to the PCM for governing fuel control of the engine.

DTC 21 Will Set When: No DTC 33 or DTC 34, TP sensor voltage is greater than

3.8 volts, engine speed is above 600 RPM, both conditions met for 10 seconds under steady throttle, road load conditions, or with throttle closed, the TP sensor should read less than.98 volt. If it doesn't, make sure cruise control and throttle cables are not being held open.

Action Taken (PCM will default to): The PCM will determine fuel and air calculations using calibrated values from a default table. The transmission will have maximum line pressure, no TCC and no 4th gear in hot mode. The MIL will become illuminated.

DTC 21 Will Clear When: A current DTC 21 will clear when a high signal voltage above the calibrated threshold is no longer detected. A history DTC 21 will clear after 50 consecutive ignition key cycles without a current DTC 21 being stored.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. With throttle closed, the TP sensor should read less than .98 volt. If it doesn't, make sure cruise control and throttle cables are not being held open.
2. With the TP sensor disconnected, the TP sensor voltage should go low, if the PCM and wiring are OK.
3. Probing C KT 47 0 with a test light checks the 5 volt return circuit. A faulty sensor ground circuit will cause a DTC 21. DTC 33, 66 or 71 may also be set.

DIAGNOSTIC AIDS

A Tech 1 scan tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT.

Also some scan tools will read: throttle angle 0% = closed throttle, 100% = WOT.

An open in CKT 470 will result in a DTC 21.

Scan TP sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from about .5 volt when throttle was closed, to about 4.8 volts when throttle is held at Wide Open Throttle (WOT) position.

Refer to "Intermittents" in "Symptoms," Section "6E3-B".

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor provides a voltage signal to the PCM that increases as the throttle blade angle increases. This signal voltage will vary from approximately .5 volt at idle to 4.8 volts at Wide Open Throttle (WOT). The TP sensor is one of the most important inputs to the PCM for governing fuel control of the engine.

DTC 22 Will Set When: TP sensor signal is less than.2 volt with engine running, and RPM greater than 400. Condition must be met for 3 seconds.

Action Taken (PCM will default to): The PCM will determine fuel and air calculations using calibrated values from a default table. The transmission will have maximum line pressure, no TCC and no 4th gear in hot mode. The MIL will become illuminated.

DTC 22 Will Clear When: A current DTC 22 will clear when a low signal voltage below the calibrated DTC 22 threshold is no longer detected. A history DTC 22 will clear after 50 consecutive ignition key cycles without a current DTC 22 being stored.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Simulates DTC 21 (high voltage): If the PCM recognizes the high signal voltage, the PCM and wiring are OK.
2. TP sensor check: The TP sensor has an auto zeroing feature. If the voltage reading is within the range of 0.29 to 0.98 volt, the PCM will use that value as closed throttle. If the voltage reading is out of the auto zero range on an existing or replacement TP sensor, check for cruise control and throttle cables for being held open.
3. This simulates a high signal voltage to check for an open in C KT 417.
4. CKT 416 is a 5 volts buffered reference signal. If CKT 416 is shorted to ground, DTC 22 will set. Be sure TP sensor is connected and clear DTC(s) before testing.

DIAGNOSTIC AIDS

A Tech 1 scan tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT.

Also some scan tools will read: throttle angle 0% = closed throttle, 100% = WOT.

An open or short to ground in CKTs 416 or 417 will result in a DTC 22.

Scan TP sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from about .5 volt when throttle was closed, to about 4.8 volts when throttle is held at Wide Open Throttle (WOT) position.

Also some scan tools will read: throttle angle 0% = closed throttle, 100% = wide open throttle.

If DTC 22 is set, check CKT 416 for faulty wiring or connections.

It is possible that any of the other sensors sharing the 5v reference line maybe causing a DTC 22 to set. Disconnect related sensors and see if DTC 22 resets.

Refer to "Intermittents" in "Symptoms," Section "6E3-B".