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Engine Sensors & Switches

NOTE: For additional sensor testing specifications, see appropriate SENSOR OPERATING RANGE CHARTS article.

Manufacturer does not provide test procedures for many individual systems and components. For sensor and switch testing not listed, perform related DTC test procedure. See appropriate SELF-DIAGNOSTICS article.

  1. Camshaft Position (CMP) Sensor (1.0L)

    A malfunction in CMP sensor circuit can set Diagnostic Trouble Code (DTC) P0340. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose CMP sensor.

    Ensure air gap measures .008-.016" (.2-.4 mm). If air gap is not as specified, align signal rotor ridge with CMP sensor. Loosen CMP sensor and adjust clearance to specification. Tighten sensor screws to 44 INCH lbs. (5 N.m). If air gap is correct, disconnect distributor 2-pin electrical connector. Measure resistance between connector terminals No. 1 (Red wire) and No. 2 (White wire). CMP sensor resistance should be 185-275 ohms at 14-122°F (-10 to 50°C). If resistance is not as specified, replace CMP sensor.

  2. Camshaft Position (CMP) Sensor (1.3L & 1.8L)

    A malfunction in CMP sensor circuit can set Diagnostic Trouble Code (DTC) P0340. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

  3. Crankshaft Position (CKP) Sensor

    A malfunction in CKP sensor circuit can set Diagnostic Trouble Code (DTC) P0335. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

  4. Electrical Load Diode Module (1.0L & 1.3L)

    Electric load diode is located under glove box, next to cigarette lighter, taped to instrument panel harness. See IDLE-UP CIRCUIT (1.0L & 1.3L)  under IDLE CONTROL SYSTEM. To test electrical load diode module circuit, see ELECTRICAL LOAD IDLE-UP CIRCUIT (1.0L & 1.3L)  under CIRCUIT TESTS.

  5. Electrical Load Idle-Up Signal (1.8L)

    Electrical load idle-up signal is received directly from taillight relay and rear defogger relay. To test electrical idle-up signal circuit, see ELECTRICAL LOAD IDLE-UP CIRCUIT (1.8L)  under CIRCUIT TESTS.

  6. Engine Coolant Temperature (ECT) Sensor

    A malfunction in ECT sensor circuit can set a related Diagnostic Trouble Code (DTC). For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. An out-of-calibration ECT sensor may not set a DTC. Use the following procedure to test sensor calibration.

    Locate and remove ECT sensor from thermostat housing. Using an ohmmeter, measure resistance of ECT sensor at specified temperatures. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE  table. If resistance is not within specification, replace ECT sensor.

    ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE (1)

    Temperature °F (°C) Ohms
    176 (80) 315
    158 (70) 435
    140 (60) 580
    122 (50) 810
    113 (45) 940
    104 (40) 1150
    95 (35) 1360
    86 (30) 1600
    77 (25) 2000
    68 (20) 2400
    59 (15) 3000
    50 (10) 3600
    41 (5) 4600
    32 (0) 5700
    23 (-5) 7400
    14 (-10) 9800
    5 (-15) 12,700
    -4 (-20) 16,000
    (1) Measure resistance across sensor terminals.

  7. Fuel Level Sensor (1.0L & 1.3L)

    A malfunction in fuel level sensor circuit can set Diagnostic Trouble Codes (DTCs) P0461 and P0463. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

  8. Fuel Tank Pressure Sensor

    See FUEL EVAPORATION  under EMISSION SYSTEMS & SUBSYSTEMS.

  9. Intake Air Temperature (IAT) Sensor

    A malfunction in IAT sensor circuit can set a related Diagnostic Trouble Code (DTC). For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. An out-of-calibration IAT sensor may not set a DTC. Use the following procedure to test sensor calibration.

    Locate and remove IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR LOCATION  table. Using an ohmmeter, measure resistance of IAT sensor at specified temperatures. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE  table. If resistance is not within specification, replace IAT sensor.

    INTAKE AIR TEMPERATURE (IAT) SENSOR LOCATION

    Application Location
    1.0L In Lower Air Cleaner Assembly
    1.3L In Air Inlet Duct
    1.8L In Air Cleaner Assembly
    INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE (1)

    Temperature °F (°C) Ohms
    176 (80) 315
    158 (70) 435
    140 (60) 580
    122 (50) 810
    113 (45) 940
    104 (40) 1150
    95 (35) 1360
    86 (30) 1600
    77 (25) 2000
    68 (20) 2400
    59 (15) 3000
    50 (10) 3600
    41 (5) 4600
    32 (0) 5700
    23 (-5) 7400
    14 (-10) 9800
    5 (-15) 12,700
    -4 (-20) 16,000
    (1) Measure resistance across sensor terminals.

  10. Knock Sensor (1.8L)

    A malfunction in Knock Sensor (KS) circuit can set Diagnostic Trouble Code (DTC) P0325. For test procedure with DTC set, see SELF-DIAGNOSTICS article. Use the following procedure to diagnose KS.
    1. Locate KS on right rear of engine block, near water pump. KS has a Black connector. Using an ohmmeter, measure resistance between KS terminal and ground. If resistance is not one megohm or greater, replace KS.
    2. Disconnect KS connector. Connect a voltmeter between KS terminal and ground. Adjust voltmeter to 200 millivolts on AC scale. Tap on engine block near KS and note reading. If no reading is present, replace KS.

  11. Heated Oxygen Sensor-1

    A malfunction in Heated Oxygen Sensor-1 (HO2S-1) circuit can set a related Diagnostic Trouble Code (DTC). For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose HO2S-1.

    A voltage is produced in response to amount of oxygen in exhaust gases. A lean mixture (high oxygen content) will produce a low voltage of about 100 mV. A rich mixture (low oxygen content) will produce a high voltage of about 900 mV. Voltage reading (activity) should vary above idle.

  12. Heated Oxygen Sensor-2

    A malfunction in Heated Oxygen Sensor-2 (HO2S-2) circuit can set a related Diagnostic Trouble Code (DTC). For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose HO2S-2.

    A voltage is produced in response to amount of oxygen in exhaust gases. A lean mixture (high oxygen content) will produce a low voltage of about 100 mV. A rich mixture (low oxygen content) will produce a high voltage of about 900 mV. Unlike HO2S-1, HO2S-2 voltage reading (activity) should seem lazy if TWC is operating properly.

  13. Manifold Absolute Pressure (MAP) Sensor

    A malfunction in MAP sensor circuit can set a related Diagnostic Trouble Code (DTC). For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose MAP sensor. If driveability problems exist, MAP sensor failure is suspected, and no DTCs are set, disconnect MAP sensor connector. If driveability improves, replace MAP sensor.
    1. Locate and remove MAP sensor. See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR LOCATION  table. Turn ignition on. Using a voltmeter, measure reference voltage from PCM to MAP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage should be about 5 volts.
    2. Disconnect vacuum hose at MAP sensor. Install a hand-held vacuum pump. Turn ignition on. Check signal voltage at MAP sensor. See appropriate wiring diagram in WIRING DIAGRAMS article.
    3. Apply vacuum and note change in signal voltage. As vacuum reading changes, signal voltage should change. Reading should be about 1.0-1.5 volts at high vacuum (idle position), or 4.0-4.5 volts at low vacuum (full throttle position).
    MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR LOCATION

    Application Location
    1.0L & 1.3L On Firewall
    1.8L On Throttle Body

  14. Park/Neutral Position (PNP) Switch (1.8L With A/T)

    A malfunction in PNP switch circuit can set Diagnostic Trouble Code (DTC) P1780. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose PNP switch.

    Disconnect PNP switch connector (located on transmission next to shift linkage). Using an ohmmeter, check for continuity between PNP switch terminals No. 2 (Black/White wire) and No. 3 (Black wire) with gearshift in Park or Neutral. Continuity should exist. If continuity does not exist in specified gear ranges, replace PNP switch.

    15. CAUTION: DO NOT use throttle stop screw to adjust TP sensor.
    Fig 1: Adjusting TP Sensor (1.0L)
    G96J09566Courtesy of GENERAL MOTORS CORP.

  15. Throttle Position (TP) Sensor (1.0L)
    A malfunction in TP sensor circuit can set Diagnostic Trouble Code (DTC) P0121, P0122 or P0123. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use the following procedure to diagnose TP sensor.
    1. Insert a .14" (3.5 mm) feeler gauge between throttle stop screw and throttle lever. See Fig 1. Check Idle Speed Control (ISC) motor plunger for contact with throttle lever screw. If ISC motor plunger is contacting throttle lever screw, engine must be brought to normal operating temperature.
    2. Install scan tool. Using scan tool, read TP sensor voltage parameter. Turn ignition on. Voltage reading should be .98-1.02 volts. If voltage is not .98-1.02 volts, adjust TP sensor. Loosen TP sensor mounting screws and turn TP sensor until voltage is as specified. Replace TP sensor if not adjustable.
    16. NOTE: TP sensor is not adjustable on 1.3L and 1.8L. Replace TP sensor as necessary.

  16. Throttle Position (TP) Sensor (1.3L & 1.8L)
    A malfunction in TP sensor circuit can set Diagnostic Trouble Code (DTC) P0121, P0122 or P0123. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

  17. Vehicle Speed Sensor (1.0L & 1.3L)

    On A/T, Vehicle Speed Sensor (VSS) is mounted on transmission case. On M/T, VSS is integral with speedometer head. A malfunction in VSS circuit can set an A/T or M/T specific Diagnostic Trouble Code (DTC) P0500. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article. Use illustration for identification of VSS terminals on M/T. See Fig 2.
    Fig 2: Identifying VSS Terminals (1.0L With M/T)
    G94C45122Courtesy of GENERAL MOTORS CORP.

  18. Vehicle Speed Sensor (1.8L)

    Vehicle Speed Sensor (VSS) is mounted on transaxle. A malfunction in VSS circuit can set Diagnostic Trouble Code (DTC) P0500. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.
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