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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 47 (Engine Controls - Tests W/Codes - 5.9L Diesel) >> Self-Diagnostic Tests >> Test NTC-4A - Checking Air Intake Heater No. 2

Test NTC-4A - Checking Air Intake Heater No. 2

WARNING: This page is about a different car, the 1995 Dodge Pickup and 1995 Dodge Cab & Chassis. 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 at the end of this article.
NOTE: If vehicle is not hard to start or does not blow Black smoke on start-up, test does not apply.
  1. Using scan tool, actuate air intake heater No. 2. While actuating heater, place scan tool in voltmeter mode. Check voltage on positive battery terminal. If voltage drops at least .5 volt when heater actuates, system is operating properly. Test is complete.
  2. If voltage does not drop at least .5 volt, listen for "clicking" noise from air intake heater relay No. 2. Relay No. 2 is rearward most of 2 air intake heater relays mounted on left front fender. If relay is clicking, perform TEST NTC-4B.
  3. If relay is not clicking, place scan tool in voltmeter mode. Check voltage on ignition 12-volt feed circuit (Light Green/Black wire) at heater relay No. 2 connector. If voltage is 10 volts or less, repair open Light Green/Black wire between heater relay and ignition switch. Perform TEST VER-1.
  4. If voltage is more than 10 volts, reconnect Light Green/Black wire connector to heater relay No. 2. Disconnect air intake heater No. 2 driver circuit (Orange/Black wire) connector from heater relay No. 2. Connect one end of a jumper wire to driver circuit terminal (where Orange/Black wire was connected) and touch other end of jumper to chassis ground.
    CAUTION: DO NOT ground jumper wire for more than 5 seconds.
  5. If air intake heater relay No. 2 does not operate, replace relay. Perform TEST VER-1. If air intake heater relay No. 2 operates, turn ignition off. Disconnect PCM connector. Using an external ohmmeter, check resistance of air intake heater No. 2 driver circuit (Orange/Black wire) between intake air heater No. 2 relay connector and PCM connector terminal No. 15. If resistance is more than 5 ohms, repair open Orange/Black wire. Perform TEST VER-1.
  6. If resistance is 5 ohms or less, place scan tool in ohmmeter mode. Check resistance of PCM connector terminal No. 15 (Orange/Black wire). If resistance is 5 ohms or less, repair short to ground in Orange/Black wire. Perform TEST VER-1. If resistance is more than 5 ohms, replace PCM. Perform TEST VER-1.
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