DTC 34

Manifold Absolute Pressure (MAP) Sensor Circuit Diagram:

CIRCUIT DESCRIPTION
The PCM applies a 5 volt reference signal, through a resistor in the PCM, to the MAP sensor. The map sensor divides the current from reference signal between a signal return to the PCM, and ground, depending on the manifold pressure. As manifold pressure increases, less current is passed along to ground, and the signal return voltage increases. The PCM monitors the signal voltage and calculates the manifold absolute pressure. The lower the engine vacuum (high absolute pressure), the higher the MAP voltage output, indicating greater demand for fuel. The higher the engine vacuum, the lower the MAP voltage output, indicating less demand for fuel. Under certain conditions (key "ON" engine not running), the MAP sensor is also used to measure barometric pressure.

Code 33 will set when:

^ Engine speed is less than 625 rpm.
^ MAP sensor signal indicates manifold pressure less than 13 kPa.
^ Both conditions exist for 0.22 second or more.

OR

^ Engine speed greater than 625 rpm.
^ TPS signal indicates throttle opening greater than 20%.
^ MAP sensor signal indicates manifold pressure less than 13 kPa.
^ All conditions exist for 0.22 second or more.

TEST DESCRIPTION

Code 34 Diagnostic Chart:

Numbers below refer to circled numbers on diagnostic chart.
1. Determines if sensor signal actually indicates conditions necessary for this code to set.
2. Connects reference voltage directly to signal circuit, checks wiring and PCM ability to read signal. If MAP voltage, as displayed on "SCAN" tool, changes to read over 4 volts, the PCM and wiring are OK.
3. This simulates a high signal voltage. Checks for open in circuit 474 and short to ground in circuit 432. If reading was less than 4 volts in previous step, and now reads more than 4 volts, then repair open or short to ground in circuit 474.

DIAGNOSTIC AIDS
^ An intermittent open or short to ground in circuit 432 will cause this code to set.

^ An intermittent open or short to ground in circuit 474 will cause this code to set. If circuit is open or shorted between splice and PCM, code 66 will also set.

^ Also Chart C-1D Manifold Absolute Pressure (MAP) Output Check for additional MAP sensor diagnostic procedures.