Test B6 - Map/BP Sensor

Fig 1: MAP/BP Tester Hook-Up

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: unusually high/low atmospheric barometer reading, kinked or blocked vacuum lines, or engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.).

1. Service Code 22. Code 22 indicates that the MAP/BP sensor is out of Self-Test voltage range (1.4-1.6 volts). Possible causes are: MAP/BP signal circuit open between sensor harness connector and ECA, MAP/BP signal circuit shorted to VREF, SIG RTN or ground, faulty MAP/BP sensor, vacuum trapped at MAP/BP sensor, high atmospheric pressure, faulty ECA or VREF or SIG RTN circuit open at sensor. Turn key off. Disconnect MAP/BP sensor from harness. Connect MAP/BP tester between wiring harness and MAP/BP sensor and connect tester to DVOM. See Fig 1 . Set DVOM on 20-volt scale. Go to next step.
2. Checking Power to MAP/BP Sensor. Green light on tester indicates VREF is okay (4-6 volts). Red light or no light on tester indicates VREF is either too low or too high. Turn key on. If Green light on tester is on, VREF is okay, go to step 4). If Green light is not on, go to next step.
3. VREF Isolation. With MAP/BP tester connected, turn key on. Disconnect MAP/BP sensor. If Green light is on, VREF is correct. Replace MAP/BP sensor and repeat QUICK TEST. If green light is not on, remove MAP/BP tester. Reconnect sensor, and go to TEST A3 - REF  . VOLTAGE, step 1).
4. MAP/BP Tester Output Reading. If accessible, measure several known good MAP sensors on available vehicles. The measured voltage will be typical for your location on day of testing. With MAP/BP tester connected and key on, measure MAP sensor voltage output. See MAP SENSOR VOLTAGE OUTPUT  table below. If voltage output is in correct range for altitude, remove MAP/BP tester and go to next step. If output reading is not within range, remove MAP/BP tester and go to step 6).
   MAP SENSOR VOLTAGE OUTPUT
   
   

   Elevation (Ft.)	Volts
   0	1.55-1.63
   1000	1.52-1.60
   2000	1.49-1.57
   3000	1.46-1.54
   4000	1.43-1.51
   5000	1.40-1.48
   6000	1.37-1.45
   7000	1.35-1.43

5. Checking MAP/BP Signal Continuity. Turn key off and wait 10 seconds. Disconnect harness from MAP/BP sensor. Disconnect ECA 60 pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAP/BP signal at sensor harness connector and test pin No. 45 at breakout box. See Fig 1 . If reading is less than 5 ohms, replace ECA. Connect ECA and MAP/BP sensor and repeat QUICK TEST. If reading is not less than 5 ohms, repair open in circuit. Remove breakout box, connect ECA and MAP/BP sensor. Repeat QUICK TEST.
6. Check MAP/BP Signal For Shorts To VREF, Signal Return And Ground. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect harness from MAP/BP sensor. Set DVOM on 200K-ohm scale. Measure resistance between test pin No. 45 and test pins No. 26, 46, 40, and 60 at breakout box. If any reading is less than 10K ohms, repair short(s) in wiring. Remove breakout box and connect ECA and MAP/BP sensor. Repeat QUICK TEST. If all readings are above 10K ohms, replace MAP/BP sensor. Remove breakout box, reconnect components and repeat QUICK TEST.
7. Service Code 22: Check for EGR Codes. Possible causes are: faulty MAP/BP sensor, faulty vacuum lines or excess EGR. If Service Codes 31, 32, 33, 34 or 35 are present, go to KOER SELF-TEST CODES, CIRCUIT TEST & STEP table in the beginning of this article and perform appropriate circuit test. If codes are not present, go to next step.
8. Checking MAP Sensor. Turn key off and wait 10 seconds. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to MAP sensor and apply 18 in. Hg vacuum to sensor. If sensor does not hold vacuum, replace sensor, connect vacuum line and repeat QUICK TEST. If MAP sensor holds vacuum, release vacuum and go to next step.
9. Attempt To Eliminate Code 22 (Engine Running). Turn key off and wait 10 seconds. Plug vacuum hose going to MAP sensor. Start engine and increase engine speed to 1400-1600 RPM. Slowly apply 15 in. Hg. vacuum to MAP sensor. While maintaining RPM, perform KOER SELF-TEST. Check for Code 22 and disregard any other codes at this time. If Code 22 is still present, replace MAP sensor, reconnect vacuum line and repeat quick test. If Code 22 is no longer displayed, inspect and repair vacuum hose going to MAP sensor. If hose is okay, service other engine running codes. If there are no codes, check engine for cause of low vacuum.
10. Service Code 72: Check Vacuum Lines. Code 72 indicates that MAP sensor output did not change enough during dynamic response ("Goose") test. Possible causes are: incorrect MAP sensor vacuum line routing or faulty MAP sensor. With key on, check vacuum lines for correct routing. Check for disconnections, kinks or blockage. Repair vacuum lines as necessary and repeat quick test. If vacuum lines are okay, go to next step.
11. Checking MAP Sensor. Turn key off and wait 10 seconds. Disconnect vacuum line from MAP sensor. Install vacuum pump to sensor and apply 18 in. Hg vacuum to sensor. If MAP sensor holds vacuum, release vacuum, remove vacuum pump, reconnect vacuum line and go to next step. If vacuum was not held, replace MAP sensor, reconnect components and repeat quick test.
12. Checking Vacuum Supply During "Goose" Test. Turn key off, wait 10 seconds. Use a "T" fitting to install a vacuum gauge in the intake manifold MAP sensor supply line. Run the KOER SELF-TEST while observing the vacuum gauge. If vacuum decreased by more than 10 in. Hg during dynamic response ("Goose") test, remove gauge, replace MAP sensor and repeat QUICK TEST. If vacuum did not decrease by 10 in. Hg or more, EEC-IV system is okay, repair engine mechanical components as necessary to increase engine vacuum.
13. Service Code 22: Continuous Test: Operating MAP/BP Sensor. Continuous Memory Code 22 indicates the MAP/BP sensor was out of Self-Test range (1.4-1.6 volts) during normal driving conditions. Possible causes are: faulty MAP/BP sensor, faulty wiring harness or connectors and unusually high or low barometric pressure. Using KOEO CONTINUOUS MONITOR TEST mode, observe test equipment while performing the following:
    • Connect a vacuum pump to the MAP/BP sensor.
    • Slowly apply 25 in. Hg vacuum to sensor.
    • Slowly bleed off vacuum from sensor.
    • Lightly tap on sensor (to simulate road shock).
    • "Wiggle" sensor connector.

    If a fault is indicated, disconnect sensor, inspect and repair connectors as necessary. If connectors are okay, replace MAP/BP sensor. If a fault is not indicated, go to next step.

14. Checking EEC-IV Harness. Stay in KOEO CONTINUOUS MONITOR (WIGGLE) TEST. Observe VOM or diagnostic tester for indication of fault while shaking, bending or wiggling small sections of harness from sensor connector to dash panel. Also check harness from dash panel to ECA in same manner. If fault is indicated, isolate fault area in harness and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.
15. Checking ECA Connector and Harness. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are not okay, repair as necessary. Repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Code 22 testing is complete.