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Code 31: Throttle Position Sensor

NOTE: Refer to illustration for ECU connector and terminal identification. See Figure .
  1. Turn ignition on. Ensure throttle valve is fully closed. Measure voltage between ECU connector E30, terminal No. 15 (backprobe) and ground. Voltage should be 4.4-5.5 volts. Measure voltage between ECU connector E30, terminal No. 4 and ground. Voltage should be .4-.5 volt. Measure voltage between ECU connector E30, terminal No. 11 and ground. No voltage should be present.
  2. Fully open throttle valve and repeat previous voltage measurements. Voltage between ECU connector E30, terminal No. 15 and ground should be 4.4-5.5 volts. Voltage between ECU connector E30, terminal No. 4 and ground should be 3.5-4.3 volts. No voltage should be present between ECU connector E30, terminal No. 11 and ground. If voltages are correct, repair ECU harness connector or replace ECU. If voltages are not correct, go to next step.
  3. Turn ignition off. Disconnect ECU and TPS connectors. Measure resistance between ECU connector E30 and TPS connector terminals. See ECU & TPS TERMINAL IDENTIFICATION table. Less than 10 ohms should be present for all measurements. Measure resistance between ground and ECU connector E30, terminals No. 15, 4 and 11. Resistance for all measurements should be at least one megohm.
    ECU & TPS TERMINAL IDENTIFICATION

    ECU Terminal TPS Terminal (Wire Color)
    No. 15 No. 1 (Black/White)
    No. 4 No. 2 (White)
    No. 11 No. 3 (Red)
  4. If resistances are not to specification, repair or replace harness connector. If resistances are to specification, check and adjust TPS. See THROTTLE POSITION SENSOR in ADJUSTMENTS article. If TPS cannot adjust correctly, replace TPS.
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