Powertrain Controls - ECM/PCM

DTC 21 - Throttle Position Sensor Circuit (Signal Voltage Low):

Throttle Position Sensor Wiring Circuit:

Circuit Description:
The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle opening. Signal voltage will vary from about .6 volt at idle to about 4.8 volts at Wide Open Throttle (WOT).

The TP sensor signal is one of the most important inputs used by the Powertrain Control Module (PCM) for fuel control and for a majority of the PCM control outputs.

DTC 22 Will Set When:

^ Engine is running.
^ TP sensor signal voltage is less than about .21 volt.
^ Above conditions are present for 5 seconds or more.

Action Taken (PCM will default to): The Malfunction Indicator Lamp (MIL) will illuminate. TP sensor Nill read 0% if engine vacuum is less than 30 kPa. TP sensor will read 10% if engine vacuum is greater than 30 kPa and vehicle speed is greater than 2 mph. The cooling fan will enable.

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

1. The TP sensor has an auto zeroing feature. If the voltage reading is within the range of about .2 to .9 volt, the PCM will use that value as closed throttle. If the voltage reading is out of the auto zero range at closed throttle, check for a binding throttle cable or damaged linkage, if OK, continue with diagnosis.
2. Simulates DTC 21: (high voltage). If the PCM recognizes the high signal voltage then the PCM 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. The Tech 1 scan tool will not read up to 12 volts, but what is important is that the PCM recognizes the signal on CKT 417

Diagnostic Aids: Scan TP sensor while depressing accelerator pedal with engine "OFF" and ignition "ON." Display should vary from about .6 volt (600 mV) when throttle is closed, to over 4.8 volts (4800 mV) when throttle is held wide open.

Also, a Tech 1 scan tool will display throttle angle %: 0% closed throttle; 100% = WOT.

If DTCs 22 and 34 are set, check CKT 416 for laulty wiring or connections.

Check condition of connector and sensor terminals for moisture or corrosion, and clean or replace as necessary. If corrosion is found, check condition of connector seal and repair or replace if necessary.

Refer to "Intermittents," in "Diagnosis By Symptom." - Intermittent Malfunctions