RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
Ignition Relay: Description and Operation
IGNITION CONTROL
Two different ignition Systems are used One type of system is used on both the 3.7L V 6 and the 4.7L V-8 engine. The other is used on the 5.9L
V-8 engine.
The 5.9L ignition system will use a conventional distributor and remotely mounted coil. The 3.7L V-6 and 4.7L V-8 engines will not use a
distributor. The 3.7L /4.7L is also equipped with separate and independent ignition coils.
3.7L V-6
The ignition system is controlled by the Powertrain Control Module (PCM) on all engines.
The 3.7L V-6 engine uses a separate ignition coil for each cylinder. The one-piece coil bolts directly to the cylinder head. Rubber boots seal the
secondary terminal ends of the coils to the top of all 6 spark plugs. A separate electrical connector is used for each coil.
Because of coil design, spark plug cables (secondary cables) are not used. A distributor is not used with the 3.7L engine.
Two knock sensors (one for each cylinder bank) are used to help control spark knock.
The Auto Shutdown (ASD) relay provides battery voltage to each ignition coil. The Powertrain Control Module (PCM) provides a ground contact
(circuit) for energizing each coil. When the PCM breaks the contact, the energy in the coil primary transfers to the secondary causing a spark. The
PCM will de-energize the ASD relay if it does not receive inputs from either the crankshaft or camshaft position sensors.
4.7L V-8
The ignition system is controlled by the Powertrain Control Module (PCM) on all engines.
The 4.7L V-8 engine uses a separate ignition coil for each cylinder. The one-piece coil bolts directly to the cylinder head. Rubber boots seal the
secondary terminal ends of the coils to the top of all 8 spark plugs. A separate electrical connector is used for each coil.
Because of coil design, spark plug cables (secondary cables) are not used. A distributor is not used with the 4.7L engine.
The Auto Shutdown (ASD) relay provides battery voltage to each ignition coil. The Powertrain Control Module (PCM) provides a ground contact
(circuit) for energizing each coil. When the PCM breaks the contact, the energy in the coil primary transfers to the secondary causing a spark. The
PCM will de-energize the ASD relay if it does not receive inputs from either the crankshaft or camshaft position sensors.
5.9L V-8
The ignition system is controlled by the Powertrain Control Module (PCM) on all engines.
The ignition system consists of:
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8 Spark Plugs
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1 Ignition Coil
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Secondary Ignition Cables
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Distributor (contains rotor and camshaft position sensor)
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Powertrain Control Module (PCM)
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Also to be considered part of the ignition system are certain inputs from the Crankshaft Position, Camshaft Position, Throttle Position and
MAP Sensors.
AUTOMATIC SHUT DOWN RELAY
PCM Output
The 5-pin, 12-volt, Automatic Shutdown (ASD) relay is located in the Power Distribution Center (PDC). Refer to label on PDC cover for
relay location.
The ASD relay supplies battery voltage (12+ volts) to the fuel injectors and ignition coil(s). With certain emissions packages it also supplies
12-volts to the oxygen sensor heating elements.
The ground circuit for the coil within the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM operates the ASD relay by
switching its ground circuit ON and OFF.
The ASD relay will be shut-down, meaning the 12-volt power supply to the ASD relay will be de-activated by the PCM if:
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the ignition key is left in the ON position. This is if the engine has not been running for approximately 1.8 seconds.
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there is a crankshaft position sensor signal to the PCM that is lower than pre-determined values.
ASD Sense - PCM Input
A 12 volt signal at this input indicates to the PCM that the ASD has been activated. The relay is used to connect the oxygen sensor heater element,
ignition coil and fuel injectors to 12 volt + power supply.
