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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 NS-3A - Inspecting Fuel Heater Relay

Test NS-3A - Inspecting Fuel Heater Relay

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.
  1. Turn ignition on. While listening for relay to click, remove and install fuel heater relay several times. If relay clicks, go to step 4). If relay does not click, go to next step.
  2. Remove fuel heater relay. Using scan tool in voltmeter mode, check voltage on fuel heater relay connector fused ignition switch output circuit (Light Green/Black wire). If voltage is less than 10 volts, repair open Light Green/Black wire. Perform TEST VER-1A. If voltage is more than 10 volts, turn ignition off.
  3. Using scan tool in ohmmeter mode, check resistance of fuel heater relay connector ground circuit (Black/Tan wire). If resistance is more than 5 ohms, repair open Black/Tan wire. PerformTEST VER-1A. If resistance is less than 5 ohms, replace fuel heater relay. PerformTEST VER-1A.
  4. Remove fuel heater relay. Using scan tool in voltmeter mode, check voltage on fuel heater relay connector fused B+ circuit (Red/Tan wire). If voltage is less than 10 volts, repair open Red/Tan wire. PerformTEST VER-1A. If voltage is more than 10 volts, turn ignition off.
  5. Disconnect fuel heater connector. Using scan tool in ohmmeter mode, check resistance of fuel heater connector ground circuit (Black/Tan wire). If resistance is more than 5 ohms, repair open Black/Tan wire. PerformTEST VER-1A.
  6. If resistance is less than 5 ohms, using an external ohmmeter, check resistance of fuel heater relay output circuit (Red/Black wire) between fuel heater relay connector and fuel heater connector. If resistance is more than 5 ohms, repair open Red/Black wire. PerformTEST VER-1A.
  7. If resistance is less than 5 ohms, ensure fuel heater temperature is less than 40°F (4.4°C). Using external ohmmeter, check resistance across fuel heater connector (component side) terminals. If resistance is less than 10 ohms, performTEST NTC-8A.
  8. If resistance is more than 10 ohms, disconnect and inspect heater element connector. Repair any damaged, pushed-out or miswired terminals. PerformTEST VER-1A. If terminals are okay, replace fuel heater. PerformTEST VER-1.
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