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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 27 (Engine Controls - Tests W/Codes - 3.0L) >> Self-Diagnostic Tests >> Test TC-4A - No Change In Map From Start To Run (DTC 13)

Test TC-4A - No Change In Map From Start To Run (DTC 13)

WARNING: This page is about a different car, the 1995 Plymouth Voyager, 1995 Plymouth Grand Voyager, 1995 Dodge Grand Caravan, and 1995 Dodge Caravan. 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 DIAGRAMS  section.
  1. Turn ignition on. Using scan tool, erase DTCs. Start engine and let idle for 30 seconds. Using scan tool, read DTCs. If scan tool displays NO CHANGE IN MAP FROM START TO RUN, go to step 8). If scan tool does not display NO CHANGE IN MAP FROM START TO RUN, go to next step.
  2. With engine still running, set engine speed to 1500 RPM using scan tool. Using scan tool, read MAP sensor voltage. While monitoring MAP sensor voltage, wiggle wiring from MAP sensor to Powertrain Control Module (PCM).
  3. If engine stalls or MAP sensor voltage becomes erratic, repair wiring or connector defect between MAP sensor and PCM. Perform TEST VER-2. If engine does not stall or MAP sensor voltage does not becomes erratic, go to next step.
  4. Using scan tool, read MAP sensor vacuum. Snap throttle open and closed. If vacuum drops rapidly to zero in. Hg, go to next step. If vacuum does not drop rapidly to zero in. Hg, go to step 7).
  5. At this time, condition required to set DTC is not present. 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. Possible causes are: ice in sensor or passage, restricted or leaking vacuum/pressure hose to MAP sensor, failed MAP sensor, or PCM failure. Go to next step.
  6. Inspect all related wiring and connectors. Repair as necessary. Perform TEST VER-2. If wiring and connectors are okay, see INACTIVE DTC CONDITION  . Perform TEST VER-2.
  7. Remove MAP sensor vacuum line and check for restriction. If a restriction is present, remove restriction and reinstall MAP sensor vacuum line. Perform TEST VER-2. If restriction is not present, replace MAP sensor. Perform TEST VER-2.
  8. Turn engine off. Connect a vacuum gauge into vacuum hose to MAP sensor. Start engine and let idle. Read vacuum gauge reading. If vacuum gauge indicates zero in. Hg at idle, repair vacuum signal to MAP sensor. If vacuum gauge does not indicate zero in. Hg at idle, go to next step.
  9. While monitoring vacuum gauge, snap throttle open and closed. If vacuum does not rapidly drop to zero in. Hg, repair restricted vacuum signal. Perform TEST VER-2.
  10. If vacuum rapidly drops to zero in. Hg, turn ignition off. Disconnect MAP sensor connector. Turn ignition on. Using scan tool in voltmeter mode, check voltage of MAP sensor connector Violet/White wire.
  11. 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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