E034

TEST CONDITIONS
1. Codes EO21, EO22, EO26, EO27, EO31, and EO32 not set;
2. Throttle switch closed;
3. RPM equal to or greater than 400;
4. TPS less than or equal to 18°;
5. BARO equal to or greater than 75 kPa.

FAILURE CONDITIONS
Difference between MAP and calculated BARO less than 11 kPa for 15 seconds.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Now" message on Driver Information Center (DIC);
3. AIR system is disabled;
4. ECM sets BARO equal to 92 kPa;
5. ECM uses substitute MAP values based on engine RPM and throttle switch status.

DESCRIPTION
The manifold absolute pressure sensor (MAP) is a "3-wire" sensor, a potentiometer that changes resistance based upon manifold vacuum. The ECM signal (CKT 432) varies between ground and 5 volts as manifold vacuum varies. As MAP decrease, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum).

The ECM uses MAP sensor values as an indication of engine load. A high MAP reading indicates a heavy load and a low MAP reading indicates a light load.
Code EO34 sets when the ECM detects a MAP sensor signal that is much too high (heavy load) for the closed throttle test conditions. Code EO34 usually indicates that there is a fault in the vacuum supply to the MAP sensor.

Notes on Fault Tree
1. MAP at idle should be 30-50 kPa, depending on engine load. BARO should be 85 to 105 kPa, depending on altitude.
2. Check for vacuum at the MAP sensor hose with a vacuum gage. At idle, typical vacuum readings are 14" - 20" Hg, depending on engine load.
3. Checking for MAP sensor or MAP circuit faults.
4. Check for broken or cracked vacuum line. Also check for MAP sensor vacuum hose restrictions.
5. Checking for sensor ground open from sensor to ECM.
6. Checking for short to voltage or sensor signal circuit (CKT 432).
7. Fault is most likely at ECM connector or ECM. Before ECM is replaced, perform "ECM replacement Check", Chart C- 1. Chart C-1 Vehicle Will Not Enter Diagnostics

Notes on Intermittents
Code EO34 is usually set by a vacuum supply problem to the MAP sensor. Check for proper vacuum routing. Also check MAP hose properly connected to the upper intake manifold, MAP hose chafed, cracked, or broken.

Apply vacuum to the MAP hose at the upper intake manifold and look for leaks in MAP hose or MAP sensor.

Manipulate affected wiring and connectors while observing ECM data ED02. Apply and release vacuum to the MAP hose using a vacuum source. If the ECM data display jumps high with vacuum applied, the failure has been induced and the cause of the intermittent can be repaired. If wiring and connectors check out ok, substitute a known good MAP sensor and retest.