1994 PCED OBDI-A | SECTION 6A: EEC-IV Pinpoint Test
Procedures |
DF: Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) Sensor |  DF: Introduction |
DF1 DIAGNOSTIC TROUBLE CODE (DTC) 22/126:
CHECK FOR POWER TO MAP/BARO SENSOR
DTC 22/126 indicates the Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) sensor is out of Self-Test range. Correct MAP/BARO range of measurement is typically from 1.4 to 1.6 volts.
Possible causes:
- MAP/BARO circuit open between sensor vehicle harness connector and PCM.
- MAP/BARO circuit shorted to VREF, SIG RTN, or GND.
- Damaged MAP/BARO sensor.
- Vacuum trapped at MAP/BARO sensor.
- High atmospheric pressure.
- Damaged PCM.
- VREF circuit open at MAP/BARO sensor.
- SIG RTN circuit open at MAP/BARO sensor.
- Key off.
- Disconnect the MAP/BARO sensor from the vehicle harness.
- Connect the MAP/BARO tester between the vehicle harness connector and the MAP/BARO sensor.
- Insert MAP/BARO tester banana plugs into DVOM.
Note: Green light on tester indicates VREF is OK (4-6 volts). Red light (or no light) indicates VREF is either too low or too high.
- Key on.
Is green light on?
DF2 CHECK FOR POWER AT SENSOR VEHICLE HARNESS CONNECTOR
Note: Green light reaffirms that VREF is OK (4-6 volts). Red light (or no light) indicates VREF is either too low or too high.
- Key on.
- MAP/BARO tester connected.
- DVOM connected to MAP/BARO tester.
- Disconnect MAP/BARO sensor.
Is green light on?
| Yes | No |
|---|
| REPLACE MAP/BARO sensor. RERUN Quick Test. | REMOVE MAP/BARO tester. RECONNECT MAP/BARO sensor. GO to Pinpoint Test Step C1. |
DF3 CHECK MAP/BARO SENSOR OUTPUT
Note: Measure several known good MAP/BARO sensors on available vehicles. The measured voltage will be typical for your location on the day of testing.
- Key on.
- MAP/BARO tester connected.
- DVOM connected to MAP/BARO tester.
- Measure MAP/BARO sensor voltage on customer vehicle.
Is DVOM voltage in range for your altitude?
| Approximate Altitude (Ft.) | Voltage Output (±.04 Volts) |
|---|
| 0 | 1.59 |
| 1000 | 1.56 |
| 2000 | 1.53 |
| 3000 | 1.50 |
| 4000 | 1.47 |
| 5000 | 1.44 |
| 6000 | 1.41 |
| 7000 | 1.39 |
| Yes | No |
|---|
| REMOVE MAP/BARO tester. GO to DF4. | REMOVE MAP/BARO tester. GO to DF5. |
DF4 CHECK MAP/BARO CIRCUIT CONTINUITY
- Key off.
- MAP/BARO sensor disconnected.
- Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
- Install breakout box, leave PCM disconnected.
- Measure resistance between MAP/BARO circuit at the MAP/BARO sensor vehicle harness connector and Test Pin 45 at the breakout box.
Is resistance less than 5.0 ohms?
| Yes | No |
|---|
| REPLACE PCM. REMOVE breakout box. RECONNECT MAP/BARO sensor. RERUN Quick Test. | SERVICE open circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test. |
DF5 CHECK MAP/BARO CIRCUIT FOR SHORTS TO VREF, SIG RTN AND GROUND
- Key off.
- MAP/BARO sensor disconnected.
- Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
- Install breakout box, leave PCM disconnected.
- Measure resistance between Test Pin 45 and Test Pins 26, 46, 40 and 60 at the breakout box.
Is each resistance greater than 10,000 ohms?
| Yes | No |
|---|
| REPLACE MAP/BARO sensor. REMOVE breakout box. RECONNECT PCM. RERUN Quick Test. | SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test. |
DF7 KEY ON ENGINE RUNNING DIAGNOSTIC TROUBLE CODE (DTC) 22/126: CHECK FOR EGR DTCs
Are KOER DTCs 326, 327, 328, 332, 334, 336 or 337 present?
| Yes | No |
|---|
| GO to EEC-IV Diagnostic Trouble Code Charts, Section 2A, for appropriate Pinpoint Test. | GO to DF8. |
DF8 CHECK MAP SENSOR OPERATION
- Key off.
- Disconnect vacuum supply hose from MAP sensor.
- Install vacuum pump to MAP sensor.
- Apply 18 in-Hg (61 kPa) vacuum to MAP sensor.
Does MAP sensor hold vacuum?
| Yes | No |
|---|
| RELEASE vacuum. GO to DF9. | REPLACE MAP sensor. CONNECT vacuum supply hose to MAP sensor. RERUN Quick Test. |
DF9 ATTEMPT TO ELIMINATE KOER DTC 22/126
- Key off.
- Plug MAP sensor vacuum supply hose.
- Start engine and maintain 1500±100 engine rpm.
- Slowly apply 15 in-Hg (51 kPa) vacuum to MAP sensor.
- While maintaining rpm, perform KOER Self-Test.
Is KOER DTC 22/126 still present?
Note: Disregard any other DTCs at this time.
| Yes | No |
|---|
| REPLACE MAP sensor. CONNECT vacuum supply hose to MAP sensor. RERUN Quick Test. | INSPECT vacuum supply hose to MAP sensor. SERVICE as necessary. If OK, SERVICE other KOER DTCs. If none, RETURN to Diagnostic Routines, Section 2A, to address any drive concerns. |
DF10 DIAGNOSTIC TROUBLE CODE (DTC) 72/129:
RERUN DYNAMIC RESPONSE TEST
Is KOER DTC 72/129 still present?
| Yes | No |
|---|
| GO to DF11. | SERVICE other DTCs as necessary. If none, testing complete. |
DF11 DIAGNOSTIC TROUBLE CODE (DTCs) 81/128:
CHECK VACUUM HOSES
Continuous Memory DTC 81/128 indicates the MAP sensor vacuum has not changed more than 2 in-Hg (7 kPa) during normal vehicle operation.
Possible causes:
- MAP sensor vacuum supply hose improper routing, blockage and/or linkage.
- MAP sensor leak.
- Key off.
- Check vacuum hoses for proper routing. Refer to VECI decal. Check MAP sensor vacuum supply hoses for disconnections, kinks or blockage.
Are vacuum hoses OK?
DF12 CHECK MAP SENSOR OPERATION
- Key off.
- Disconnect vacuum supply hose from MAP sensor.
- Install vacuum pump to MAP sensor.
- Apply 18 in-Hg (61 kPa) vacuum to MAP sensor.
Does MAP sensor hold vacuum?
| Yes | No |
|---|
| RELEASE vacuum. REMOVE vacuum pump. RECONNECT vacuum supply hose to MAP sensor. GO to DF13. | REPLACE MAP sensor. RECONNECT vacuum supply hose to MAP sensor. RERUN Quick Test. |
DF13 CHECK THAT VACUUM TO MAP SENSOR DECREASES DURING DYNAMIC RESPONSE
- Key off.
- Tee a vacuum gauge in the intake manifold vacuum supply hose at the MAP sensor.
- Perform KOER Self-Test while observing vacuum.
Did vacuum decrease by more than 10 in-Hg (34 kPa) vacuum during Dynamic Response test?
| Yes | No |
|---|
| REPLACE MAP sensor. REMOVE vacuum gauge. RERUN Quick Test. | EEC system OK. REFER to Engine Service Manual Group for probable causes affecting engine vacuum. |
DF90 CHECK FOR CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 22/126:
EXERCISE MAP/BARO SENSOR
Continuous Memory DTC 22/126 indicates the Manifold Absolute Pressure (MAP)/Barometric Pressure (BARO) sensor was out of self-test range. The code was set during normal driving conditions. Correct range of measurement is typically from 1.4 to 1.6 volts.
Possible causes:
- Damaged MAP/BARO sensor.
- Damaged EEC vehicle harness.
- Damaged MAP/BARO sensor vehicle harness connectors and/or terminals.
- Unusually high/low barometric pressure.
- Using Key On, Engine Off Continuous Monitor Diagnostic Test Mode (DTM), observe VOM or STAR LED for indication of a fault while performing the following:
- Connect a vacuum pump to the MAP/BARO sensor.
- Slowly apply 84 kPa (25 in-Hg) vacuum to the MAP/BARO sensor.
- Slowly bleed vacuum off the MAP/BARO sensor.
- Lightly tap on MAP/BARO sensor (simulate road shock).
- Wiggle MAP/BARO connector.
Is fault indicated?
| Yes | No |
|---|
| DISCONNECT and INSPECT connectors. If connector and terminals are good, REPLACE MAP/BARO sensor. RERUN Quick Test. | GO to DF91. |
DF91 CHECK EEC VEHICLE HARNESS
- Remain in Key On, Engine Off Continuous Monitor DTM.
- Observe VOM or STAR LED for a fault indication while performing the following:
- Referring to the illustration in Step DF90, grasp the vehicle harness closest to the sensor connector. Wiggle, shake or bend a small section of the EEC system vehicle harness while working toward the dash panel. Also wiggle, shake or bend the EEC vehicle harness from the dash panel to the PCM.
Is a fault indicated?
| Yes | No |
|---|
| ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory Code (REFER to Quick Test Appendix, Section 5A). RERUN Quick Test. | GO to DF92. |
DF92 CHECK PCM AND VEHICLE HARNESS CONNECTORS
- Key off.
- Disconnect PCM 60 pin connector.
- Inspect connectors and connector terminals for obvious damage or faults.
Are connectors and terminals OK?
| Yes | No |
|---|
| SERVICE as necessary. RERUN Quick Test. | Unable to duplicate and/or identify fault at this time. For further diagnosis, REFER to Section 7A, Intermittent Fault Diagnosis. All others, CLEAR Continuous Memory (REFER to Quick Test Appendix, Section 5A). RERUN Quick Test. |