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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (Engine Controls - Tests W/Codes - 2.5L) >> Self-Diagnostic Tests >> Test TC-6A - No Change In Map From Start To Run And Slow Change In Idle Map Sensor Signal (DTC 13)

Test TC-6A - No Change In Map From Start To Run And Slow Change In Idle Map Sensor Signal (DTC 13)

WARNING: This page is about a different car, the 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagrams, see WIRING DIAGRAM  section.
  1. Turn ignition on with engine off. Using scan tool, read DTCs. If scan tool displays MAP SENSOR VOLTAGE TOO LOW, go to TC-4A. If scan tool does not display MAP SENSOR VOLTAGE TOO LOW, go to next step.
  2. Using scan tool, erase DTCs. Start engine. Allow engine to idle for 30 seconds. With engine running, use scan tool read DTCs. If scan tool displays NO CHANGE IN MAP FROM START TO RUN or SLOW CHANGE IN IDLE MAP SENSOR SIGNAL, go to step 9).
  3. If scan tool does not display NO CHANGE IN MAP FROM START TO RUN or SLOW CHANGE IN IDLE MAP SENSOR SIGNAL, use scan tool to set engine speed to 1500 RPM. With engine running at 1500 RPM, read scan tool MAP sensor voltage. While monitoring MAP sensor voltage, wiggle MAP sensor connector and wiring harness while watching scan tool display.
  4. If engine stalls or MAP sensor voltage becomes erratic, inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If engine does not stall and MAP sensor voltage does not become erratic, snap throttle open and closed while monitoring scan tool.
  5. If engine vacuum does not rapidly drop to less than one in. Hg, go to step 8). If engine vacuum rapidly drops to less than one in. Hg, condition required to set DTC is not present at this time. See steps 6) and 7) for conditions and cause of SLOW CHANGE IN IDLE MAP SENSOR SIGNAL DTC and NO CHANGE IN MAP FROM START TO RUN DTC.
  6. SLOW CHANGE IN IDLE MAP SENSOR SIGNAL DTC sets if following conditions exist: MAP sensor signal is less than .157 volt between firing pulses of engine and engine speed is more than 600 RPM but less than 1500 RPM. Check for following possible causes: restricted passage to MAP sensor, ice in MAP sensor or passage, MAP sensor failure or failed PCM. Perform TEST VER-2.
  7. NO CHANGE IN MAP FROM START TO RUN DTC sets if difference between barometric pressure (ignition on) and manifold absolute pressure (engine running for 1.72 seconds) is too small. Check following for possible causes: restricted or leaking vacuum/pressure hose to MAP sensor, ice in MAP sensor or passage, MAP sensor failure or failed PCM. Perform TEST VER-2.
  8. Remove MAP sensor vacuum hose. Inspect condition of MAP sensor vacuum hose. If MAP sensor vacuum hose is restricted or open, replace vacuum hose as necessary. Perform TEST VER-2. If MAP sensor vacuum hose is okay, replace MAP sensor. Perform TEST VER-2.
  9. Turn engine off. Tee a vacuum gauge into MAP sensor vacuum hose. Start engine. With engine idling, read vacuum gauge. If vacuum gauge reads zero in. Hg, repair vacuum hose to MAP sensor. Perform TEST VER-2.
  10. If vacuum gauge does not read zero in. Hg, snap throttle open and closed while monitoring vacuum gauge. If vacuum gauge reading does not rapidly drop to less than one in. Hg, replace MAP sensor vacuum hose as necessary. Perform TEST VER-2.
  11. If vacuum gauge reading rapidly drops to less than one in. Hg, turn ignition off. Disconnect MAP sensor electrical connector. Turn ignition on. Put scan tool in voltmeter mode. Using scan tool, check voltage on MAP sensor connector Violet/White wire.
  12. If voltage is less than 4 volts, repair open or shorted Violet/White wire. Perform TEST VER-2. If voltage is more than 4 volts, replace MAP sensor. Perform TEST VER-2.
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