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HOMESERVICE MANUALSCHEVROLET1998SUBURBAN K2500, 7.4 J, PART TIMEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 257 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0105: MAP SENSOR CIRCUIT RANGE/PERFORMANCEDIAGNOSTIC PROCEDURES
1998 Chevrolet Suburban K2500, 7.4 J, Part Time

Diagnostic Procedures

1998 Chevrolet Suburban K2500, 7.4 J, Part TimeSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Inspect for vacuum hoses that are disconnected, damaged, or incorrectly routed. Inspect MAP sensor seal missing or damaged, restrictions in MAP sensor vacuum source, or intake manifold vacuum leaks. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
    3. NOTE: The vehicle used for the comparison is not limited to the same type of vehicle as is being serviced. A vehicle known to provide an accurate reading is acceptable.
  3. Do you have access to another vehicle in which the MAP sensor pressure can be observed with a scan tool? If yes, go to next step. If no, go to step  5.
  4. Turn ignition on, with engine off. Observe the MAP sensor pressure with a scan tool. Observe the MAP sensor pressure in the known-good vehicle with a scan tool. Compare the values. Is the difference between the values less than 3 kPa? If yes, go to step  6. If no, go to step  11.
    5. NOTE: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Refer to SENSOR OPERATING RANGE CHARTS - TRUCKS article. Weather conditions consisting of very low or very high pressure and/or very low or very high temperature may cause a reading to be slightly out of range.
  5. Turn ignition on, with engine off. Observe the MAP sensor pressure with a scan tool. Refer to SENSOR OPERATING RANGE CHARTS - TRUCKS article. The MAP sensor pressure should be within the range specified for your altitude. Does the MAP sensor indicate the correct barometric pressure? If yes, go to next step. If no, go to step  11.
  6. Observe the MAP sensor pressure with a scan tool. Start engine. Does the MAP sensor pressure change? If yes, go to next step. If no, go to step  11.
  7. Turn ignition off. Remove the MAP sensor from the intake manifold. Leave the MAP sensor connected to the electrical harness. Connect a hand-held vacuum pump to the MAP sensor port. Turn ignition on, with engine off. Observe the MAP sensor pressure with the scan tool. Apply vacuum to the MAP sensor with vacuum pump in 1 in. Hg increments until 15 in. Hg is reached. Each 1 in. Hg should decrease MAP sensor pressure by 3-4 kPa. Is the decrease in MAP sensor pressure consistent? If yes, go to next step. If no, go to step  11.
  8. Observe the MAP sensor pressure with the scan tool. Apply vacuum with the hand vacuum pump until 20 in. Hg is reached. Is the MAP sensor pressure less than 34 kPa? If yes, go to next step. If no, go to step  11.
  9. Observe the MAP sensor pressure with scan tool. Disconnect the vacuum pump from the MAP sensor. Does the MAP sensor pressure return to the original reading observed in step  4 or  5 ? If yes, go to next step. If no, go to step  23.
  10. Check for incorrect cam timing, restricted exhaust flow, or worn piston rings. Did you find and correct the condition? If yes, go to step  25. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L & 3.0L VUE article.
  11. Disconnect the MAP sensor electrical connector. Observe the MAP sensor voltage with the scan tool. Is the voltage less than 0.1 volt? If yes, go to next step. If no, go to step  16.
  12. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DVOM. Is the voltage greater than 5.2 volts? If yes, go to step  17. If no, go to next step.
  13. Probe the 5-volt reference circuit of the MAP sensor with a test light that is connected to a good ground. Is the test light off? If yes, go to step  18. If no, go to next step.
  14. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. Observe the MAP sensor voltage with the scan tool. Is the voltage greater than 4.9 volts? If yes, go to next step. If no, go to step  19.
  15. Turn ignition off. Remove jumper wire. Connect a jumper wire between each of the terminals in the MAP sensor harness connector and the corresponding terminal at the MAP sensor. Turn ignition on, with engine off. Measure the voltage from the low reference circuit of the MAP sensor at the jumper wire terminal to a good ground with a DVOM. Is the voltage greater than 0.2 volt? If yes, go to step  20. If no, go to step  21.
    16. NOTE: Disconnecting the ECM may eliminate the short during testing.
  16. Test MAP sensor signal circuit between the ECM and MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
    17. NOTE: Disconnecting the ECM may eliminate the short during testing.
  17. Test all of the branches of the 5-volt reference circuit that are shared with the MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  18. Test 5-volt reference circuit between the ECM and MAP sensor for an open or for high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  19. Test MAP sensor signal circuit between the ECM and MAP sensor for a short to ground, an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  20. Test low reference circuit between the ECM and MAP sensor for an open or for high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  21. Test for an intermittent and for a poor connection at the MAP sensor. Did you find and correct the condition? If yes, go to step  25. If no, go to step  23.
  22. Test for an intermittent and for a poor connection at the ECM. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  23. Replace MAP sensor. After replacing sensor, go to step  25.
  24. Turn ignition off. Replace ECM. Perform ECM relearn procedure. See ELECTRONIC CONTROL MODULE REPROGRAMMING  under PROGRAMMING. After replacing ECM, go to next step.
  25. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within the conditions for running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate vehicle within the conditions observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  26. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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