Diagnostic Aids

Perform this test when directed by QUICK TEST. This system test is intended to diagnose:

Barometric Pressure (BARO) Sensor
Wiring Harness Circuits (BARO SIG, SIG RTN & VREF)
Powertrain Control Module (PCM)

1) DTC P0106, P0107, P0108 Or P0109

Obtain local barometric pressure measurement. Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select BARO PID from PID/DATA MONITOR & RECORD menu. Compare BARP PID readings with specifications in table. See BARO SENSOR SPECIFICATIONS table. If BARO PID value is within specification, problem is not present at this time, go to TEST Z, step 1). If BARO PID value is not within specification, go to next step.

BARO SENSOR SPECIFICATIONS

In. Hg (kPa)	Frequency (Hz)
17.1 (58)	122.4
18.3 (62)	125.5
19.5 (66)	128.7
20.7 (70)	131.9
21.8 (74)	135.1
23.0 (78)	138.3
24.2 (82)	141.8
25.4 (86)	145.4
26.6 (90)	148.9
27.7 (94)	152.5
28.9 (98)	156.1
30.1 (102)	159.6
31.0 (105)	162.4

2) Check BARO Signal & SIG RTN Circuits For Open

Using a DVOM, measure resistance of BARO circuit between PCM harness connector terminal and BARO sensor harness connector terminal. See Fig 1. Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector terminal and BARO sensor harness connector terminal. If resistance in either measurement is 5 ohms or more, repair open circuit. If resistance in both measurements is less than 5 ohms, perform the following:
- For DTC P0108, go to step 7).
- All others, go to next step.
Fig 1: Identifying BARO Sensor Circuits & Connector Terminals
Courtesy of FORD MOTOR CO.

3) Check VREF Voltage To BARO Sensor

Disconnect BARO sensor connector. Using a DVOM, measure voltage between BARO sensor harness connector VREF and STG RTN terminals. See Fig 1. If voltage is 4-6 volts, go to step 5). If voltage is not 4-6 volts, go to next step.

4) Check VREF Circuit For Open

Using a DVOM, measure resistance of VREF circuit between PCM harness connector terminal and BARO sensor harness connector terminal. See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open VREF circuit.

5) Check BARO Circuit For Short To Ground

Ensure ignition switch is turned to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance between PCM harness connector BARO and SIG RTN terminals. See Fig 1. Using a DVOM, measure resistance between PCM harness connector BARO terminal and negative battery terminal. If both resistance measurements are more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, repair short in affected circuit.

6) Check VREF Circuit For Short To Ground

Using a DVOM, measure resistance between PCM harness connector VREF and SIG RTN terminals. See Fig 1. Using a DVOM, measure resistance between PCM harness connector VREF terminal and negative battery terminal. If either resistance measurement is 10 k/ohms or less, repair short to ground in affected circuit. If both resistance measurements are more than 10 k/ohms, replace BARO sensor. If problem is still present, replace PCM.

7) DTC P0108: Induce Opposite Code

Disconnect BARO sensor electrical connector. Turn ignition switch to ON position. Check for DTCs. If DTC P0107 is present, replace BARO sensor. If DTC P0107 is not present, go to next step.

8) Check BARO Signal Circuit For Short To Power

Turn ignition switch to OFF position. Using a DVOM, measure resistance between PCM harness connector BARO and VPWR terminals. See Fig 1. If resistance measurement is more than 10 k/ohms, replace PCM. If resistance measurement is 10 k/ohms or less, repair short to VPWR in BARO circuit.