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Test H - Map Sensor

NOTE: Barometric pressure sensor output is digital and must be measured with MAP/BP tester.

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, engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.).

  1. Code 22 Displayed, Engine Off. Turn key off. Disconnect MAP sensor from harness. Connect MAP/BP tester between wiring harness and MAP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. See Fig 1 . Go to next step.
    Fig 1: MAP/BP Tester Hook-Up
    G2547
  2. With MAP/BP tester connected, turn key on. If only Green light on tester is lit, VREF is correct. Go to step 4). If "LESS THAN 4 VOLTS" Red light or no lights come on, VREF is too low. If "MORE THAN 6 VOLTS" Red light comes on, VREF is too high. If VREF is too high or too low, go to next step.
  3. With MAP/BP tester connected, turn key on. Disconnect MAP sensor. Repeat step 2). If only Green light comes on, VREF is correct. Replace MAP sensor. Repeat QUICK TEST  . If "LESS THAN 4 VOLTS" Red light or no lights come on, VREF is too low. If "MORE THAN 6 VOLTS" Red light comes on, VREF is too high. If VREF is too high or too low, remove tester, connect sensor, then go to TEST C - REFERENCE VOLTAGE  , step 1).
  4. With MAP/BP tester connected and key on, measure sensor output voltage. If voltage output is in correct range for altitude of vehicle being tested, remove MAP/BP tester and go to next step. If output reading is outside range, remove tester and go to step 6).
    NOTE: Measure several known good MAP sensors on available vehicles. Mean voltage reading will be typical for your location on date of testing.
    MAP VOLTAGE OUTPUT SPECIFICATIONS

    Elevation (Ft.) Voltage Output (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. Turn key off and wait 10 seconds. Disconnect MAP sensor from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAP signal at sensor connector and test pin No. 45. If reading is less than 5 ohms, replace ECA. Connect ECA and MAP sensor and repeat QUICK TEST  . If reading is 5 ohms or higher, repair opens in wiring. Remove breakout box, connect ECA and MAP sensor. Repeat QUICK TEST  .
  6. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect harness at MAP sensor. Set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 45 and test pins No. 26, 46, 40, and 60. If any reading is less than 10,000 ohms, repair shorts in wiring. Remove breakout box and connect ECA and MAP sensor. Repeat QUICK TEST  . If all readings are 10,000 ohms or more, replace MAP sensor. Remove breakout box and connect all wiring. Repeat QUICK TEST  .
  7. Code 22 Displayed, KEY ON/ENGINE RUNNING (KOER) . Check to see if service codes 31, 32, 33, 34 or 35 are present. If so, go to KOER SELF-TEST table and perform appropriate CIRCUIT TEST  . If not, go to next step.
  8. 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 does hold vacuum, release vacuum and go to next step.
  9. Turn key off and wait 10 seconds. Plug vacuum hose going to MAP sensor. Start engine and run at 1400-1700 RPM. Slowly apply 15 in. Hg. vacuum to MAP sensor. With engine under these operating conditions, perform KOER SELF-TEST. If code 22 is still present, replace MAP sensor. If code 22 is no longer displayed, inspect vacuum hose going to MAP sensor. If okay, service other codes. If there are none, check engine for cause of low vacuum.
  10. Code 72 Displayed. Turn key off and wait 10 seconds. Install vacuum gauge with "T" in manifold vacuum line at MAP sensor. Perform KOER SELF-TEST and observe vacuum reading before and during DYNAMIC RESPONSE CHECK portion of test. Record service codes. If vacuum decreased 10 in. Hg or more and code 72 is not displayed, disconnect vacuum gauge and service other codes as necessary. If vacuum decreased 10 in. Hg and code 72 is displayed, replace MAP sensor and repeat QUICK TEST  . If vacuum decreased less than 10 in. Hg, go to next step.
  11. Check vacuum lines for correct routing, using vehicle emissions decal as a guide. Also check MAP sensor vacuum lines for kinks or blockage. If lines are good, EEC-IV system is okay. Check engine for cause of low vacuum. If vacuum lines are bad, repair as necessary and repeat step 9).
  12. Turn key off. Disconnect MAP sensor from harness. Connect MAP/BP tester between wiring harness and MAP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. See MAP/BP Tester Hook-Up. Go to next step.
  13. Turn key on and measure sensor output. Compare values to MAP VOLTAGE OUTPUT  table. If reading is within range, go to next step. If reading is out of range, replace MAP sensor. Repeat QUICK TEST  .
  14. Check map sensor vacuum lines for leaks, bad connections, kinks or blockage. If vacuum lines are okay, go to DIAGNOSIS BY SYMPTOM TEST  . If vacuum lines are bad, repair as necessary and repeat QUICK TEST  .
  15. Continuous Code 22 Displayed. Using CONTINUOUS MONITOR (WIGGLE) TEST, observe VOM or diagnostic tester for indication of fault while doing the following: connect vacuum pump to MAP sensor and slowly apply 25 in. Hg. Bleed vacuum slowly, tap MAP sensor lightly, and wiggle MAP connector. If fault is indicated, disconnect sensor. Inspect connector and terminals for damage. If connector and terminals are okay, replace MAP sensor and repeat QUICK TEST  . If no fault is indicated, go to next step.
  16. Stay in 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 firewall. Check harness from firewall to ECA in same manner. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST  . If no fault is indicated, go to next step.
  17. 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.
Fig 2: MAP Sensor Circuit
G2548
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