Diagnostic Procedure

CAUTION: To prevent damage to scan tool always turn ignition switch to LOCK position before connecting or disconnecting scan tool.

Using scan tool check BARO sensor. Connect scan tool to data link connector. Turn ignition on. Set scan tool to the data reading mode for data list item 25: BAROMETRIC PRESSURE SENSOR. Check scan tool output. See BAROMETRIC PRESSURE SENSOR PRESSURE OUTPUT table. Turn ignition switch to LOCK position. If sensor is not operating properly, go to next step. If sensor is operating properly, malfunction is intermittent.

BAROMETRIC PRESSURE SENSOR PRESSURE OUTPUT

Altitude - Feet (Meters)	Scan Tool Output (kPa)
0 (0)	101
1969 (600)	95
3937 (1200)	88
5906 (1800)	81

Do not disconnect BARO sensor harness connector. Turn ignition on. Using a DVOM, measure voltage between BARO sensor harness connector terminal No. 2 and ground by backprobing. See BAROMETRIC PRESSURE SENSOR VOLTAGE OUTPUT table. If voltage is as specified, go to next step. If voltage is not as specified, go to step 5 .

BAROMETRIC PRESSURE SENSOR VOLTAGE OUTPUT

Altitude - Feet (Meters)	Voltage
0 (0)	3.7-4.3
1969 (600)	3.4-4.0
3937 (1200)	3.2-3.8
5906 (1800)	2.9-3.5

Check BARO sensor harness connector and ECM harness connector C-115 (M/T) or PCM harness connector C-118 (A/T) for damage. Repair or replace as necessary. After repairs, go to step 12 . If connectors are okay, go to next step.
Turn ignition on. Using scan tool, check BARO sensor. Set scan tool to the data reading mode for data list item 25: BAROMETRIC PRESSURE SENSOR. Check scan tool output. See BAROMETRIC PRESSURE SENSOR PRESSURE OUTPUT table. If sensor is not operating properly, replace ECM or PCM. After replacing ECM or PCM, go to step 12 . If sensor is operating properly, malfunction is intermittent.
Do not disconnect BARO sensor. Turn ignition on. Using DVOM, measure voltage between BARO sensor harness connector terminal No. 1 and ground by backprobing. Voltage reading should be 4.8-5.2 volts. Turn ignition switch to LOCK position. If voltage is not as specified, go to next step. If voltage is as specified, go to step 7 .
Check ECM harness connector C-115 (M/T) or PCM harness connector C-118 (A/T) for damage. Repair or replace as necessary. After repairs, go to step 12 . If connector is okay, replace ECM or PCM. After replacing ECM or PCM, go to step 12 .
Do not disconnect BARO sensor harness connector. Turn ignition on. Using DVOM, measure voltage between sensor harness connector terminal No. 5 and ground by backprobing. Voltage should be 0.5 volt or less. If voltage is not as specified, go to next step. If voltage is as specified, go to step 10 .
Check BARO sensor harness connector and ECM harness connector C-119 (M/T) or PCM harness connector C-120 (A/T) for damage. Repair or replace as necessary. After repairs, go to step 12 . If connector is okay, go to next step.
Check for open circuit between BARO sensor harness connector terminal No. 5 and ECM harness connector C-119 terminal No. 40 (M/T) or PCM harness connector C-120 terminal No. 16 (A/T). Repair as necessary, go to step 12 . If wiring harness is okay, replace ECM or PCM. After replacing ECM or PCM, go to step 12 .
Check BARO sensor harness connector sensor for damage. Repair or replace as necessary. After repairs, go to step 12 . If connector is okay, go to next step.
Check ECM harness connector C-119 (M/T) or PCM harness connector C-120 (A/T) for damage. Repair or replace as necessary. After repairs, go to next step. If connector is okay, replace VAF sensor. After replacing sensor, go to next step.
Test the OBD-II drive cycle. Carry out a test drive with the drive cycle pattern. See OTHER MONITOR under VERIFYING REPAIRS. Check for DTCs. If DTC P0108 is output, repeat diagnosis. If DTC P0108 is not output, inspection is complete.