Powertrain Controls - ECM/PCM

CIRCUIT DESCRIPTION
The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle valve. Signal voltage will vary from less than 1.0 volt at idle to about 4.5 volts at wide open throttle (WOT).

The TPS signal is one of the most important inputs used by the ECM for fuel control and for many of the ECM controlled outputs.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. Code 22 will set if:
^ Engine is running.
^ TPS signal voltage is less than 0.2 volt for 4 seconds.
2. Simulates Code 21: (high voltage). If ECM recognizes the high signal voltage the ECM and wiring are OK.
3. With closed throttle, ignition "ON" or at idle, voltage at "GF13" should be 0.36-0.44 volt. If not, replace the TPS. See "Electronic Control Module" for replacement procedures.
4. Simulates a high signal voltage. Checks CKT 417 for an open.

DIAGNOSTIC AIDS
A "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 Code 22.
^ Poor Connection or Damaged Harness. Inspect ECM harness connectors for backed out terminal "GFl3," improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Intermittent Test If connections and harness check OK, monitor TPS voltage display while moving related connectors and wiring harness. If the failure is induced, the display will change. This may help to isolate the location of the malfunction.
^ TPS Scaling. Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from closed throttle TPS voltage when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at wide open throttle position.