E034

ECM Code E034:

DFI Sensor Circuit:

DESCRIPTION:

The MAP sensor output voltage is a DC voltage that varies with Manifold Absolute Pressure (MAP). As MAP decreases, voltage on CKT 432 decreases (low engine load, high engine vacuum). As MAP increases, voltage on CKT 432 increases (high engine load, low engine vacuum). The ECM uses the MAP sensor reading as an indicator of engine load. Low MAP readings mean low engine load, high MAP readings mean high engine load. Code E034 is designed to set when the ECM detects a MAP sensor signal that is much too high for the closed throttle test conditions. Code E034 usually indicates that there is a fault in the vacuum supply to the MAP sensor.

TEST CONDITIONS:

1. Codes E021, E022, E026, E027, E031, and E032 clear.
2. Key on.
3. Engine speed greater than or equal to 400 RPM.
4. Throttle switch closed.
5. TPS less than or equal to 12 degrees.
6. BARO greater than or equal to 68 kPa.

FAILURE CONDITIONS:

MAP value within 6 kPa of the BARO value for 2.1 seconds.

ACTION TAKEN:

1. The ECM illuminates the "SERVICE ENGINE SOON" telltale.
2. ECM commands BCM to display "SERVICE CAR SOON" message on CCDIC.
3. ECM turns off both air management solenoids.
4. ECM uses a substitute MAP sensor value of 81.8 kPa with throttle switch open.
5. ECM looks up a substitute MAP sensor value from a table of "Substitute MAP" vs. RPM when the throttle switch is closed.

NOTES ON FAULT TREE:

1. MAP at idle should be 30 to 50 kPa, depending on engine load. BARO should be 85 to 105 kPa, depending upon altitude.

2. Check for vacuum at the MAP sensor hose with a vacuum gauge. At idle, typical vacuum readings are 15" to 20" Hg, depending on engine load.

3. Vacuum supply to sensor is OK, checking for MAP sensor or MAP circuitry fault.

4. Checking for sensor ground open from sensor to ECM.

5. Checking for a short to voltage on sensor signal, CKT 432.

6. Fault is most likely at ECM connector or ECM. Before replicing the ECM, perform the "ECM Replacement Check", CHART C-1.

NOTE ON INTERMITTENTS:

Code E034 is usually set by a vacuum supply problem to the MAP sensor. Check for proper vacuum routing (see emission label underhood), for MAP hose connected to the proper throttle body port, MAP hose chafed, pinched, or cut. Apply vacuum to the MAP hose at the throttle body and look for vacuum leaks in the MAP hose or MAP sensor. Manipulate affected wiring and connections while observing ECM parameter ED02. Apply and release vacuum to the MAP hose at the throttle body using a vacuum source. If the ECM parameter ED02 jumps or skips high with vacuum applied, the condition has been induced and the cause of the intermittent and be repaired. If wiring and connectors check out OK, substitute a known good MAP sensor and retest.

Review the snapshot data parameters stored with this code to verify failure condition. If the failure condition is verified, check and repair intermittent wiring connection, or sensor.