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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 101 (Engine Controls - System/Component Tests - 5.9L Diesel) >> Emission Systems & Sub-Systems >> Intake Manifold Air Heater System >> Intake Manifold Air Heater Preheat/Postheat Cycle

Intake Manifold Air Heater Preheat/Postheat Cycle

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. Air temperature at intake manifold must be less than 59°F (15°C). Turn ignition on. The WAIT-TO-START light on instrument panel should come on. A click should be heard from the intake manifold air heater relays, indicating preheat cycle has begun (relays are located in engine compartment, near left battery). See Figure .
  2. Measure voltage at both terminals of intake manifold air heater, located between air inlet housing and intake manifold cover. Battery voltage should exist at both terminals for 10-30 seconds, depending on intake air temperature. See HEAT CYCLE SPECIFICATIONS table.
HEAT CYCLE SPECIFICATIONS

Intake Air Temperature Preheat Cycle With Ignition On & Engine Off Postheat Cycle With Ignition On & Engine On
Greater Than 59°F (15°C) 0.0 Seconds No
15°F (-10°C) To 59°F (15°C) 10.0 Seconds Yes
0°F (-18°C) To 15°F (-10°C) 15.0 Seconds Yes
Below 0°F (-18°C) 30.0 Seconds Yes