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Home >> Chevrolet >> 1988 >> Cavalier VL, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> 2.0L VIN [1] TBI CEC Tests W/Codes >> Code 34: Map Sensor Signal Volt Lo >> Notes

Code 34: Map Sensor Signal Volt Lo: Notes

The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1-1.5 volts at closed throttle idle, to 4-4.5 volts at wide open throttle. If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the Throttle Position Sensor (TPS) to control fuel delivery.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test determines if Code 34 is the result of a hard failure or an intermittent condition. A Code 34 will set when the following conditions occur:
    • MAP signal voltage is too low.
    • The engine speed is greater than 1200 RPM.
    • TPS signal greater than 15 percent
  2. By jumping harness terminals "B" to "C", and with 5 volts to signal, this will determine if the sensor is at fault, or if there is a problem with the ECM or wiring.
  3. The "Scan" tester may not display 12 volts. The important thing is that the ECM recognizes the voltage as more than 4 volts, indicating that the ECM and circuit No. 432 are okay.
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