Ram B1500, B2500, B3500, 1999-2003

4.7L Engine


For information on understanding electricity and troubleshooting electrical circuits, please refer to the "CHASSIS ELECTRICAL" section.

Diagnosis & Testing

Component tests are limited to checks of the spark plugs and coils. Specialized analysis equipment is needed for more in-depth troubleshooting.

Do NOT run the engine with a coil disconnected. Do NOT attempt to ground a coil to the engine to check for spark. Sensitive components could be ruined or the extremely high voltage could cause serious injury or death.

General Information

The 4.7L V-8 engine uses an advanced distributorless ignition system. A dedicated ignition coil is mounted above each spark plug and bolted to the engine. No plug wires are employed.

The main components of the ignition system are:

Powertrain control module (PCM)
Ignition coils
Spark plugs
Crankshaft and camshaft position sensors.

The PCM automatically regulates the spark advance to fire the spark plugs according to input from various engine sensors. The input signals are then used to compute the optimum ignition timing for the lowest exhaust emissions and best driveability. During the crank-start period, ignition timing advance is set to ensure quick and efficient starting.

The amount of electronic spark advance provided is determined by four input factors: coolant temperature, engine rpm, throttle position and available manifold vacuum. On some late model systems, intake manifold temperature is also used. Gear selection may also be a factor.

Battery voltage is supplied to each coil by the Automatic Shutdown (ASD) relay. The PCM opens and closes each coil's ground circuit at a specific time to fire the plug.

By controlling the coil ground circuit, the PCM is able to set the base timing and adjust the ignition timing advance. This is done to meet changing engine conditions.

Base ignition timing is set by the PCM and is not adjustable.

Click image to see an enlarged view

Fig. Ignition coil components on the 4.7L engine. Primary winding resistance is measured at the electrical connector terminals

Ignition Coil

Removal & Installation
  1. Certain coils may require removal of the throttle body air intake tube or intake box for access.
  3. Disconnect the negative battery cable.
  5. Detach the electrical connector from the coil by pushing downward on the release lock on top of the connector and pulling the connector from the coil.
  7. Clean the area at the base of each coil with compressed air.
  9. Remove the coil mounting nut. Pull the coil up with a slight twisting action and remove it from the vehicle.
  11. Installation is the reverse of removal. Smear the coil O-ring with silicone grease. Tighten the mounting nut to 70 inch lbs. (8 Nm). Connect the wiring.


The coil(s) can be checked with an ohmmeter.

  1. Disconnect the negative battery cable.
  3. Remove the coil from the engine.
  5. Primary winding resistance (across the low tension terminals) should be 0.6-0.9 ohms.
  7. Secondary winding resistance (across the spark plug lead and one of the low tension terminals) should be 6-9 kilo-ohms.
  9. Replace any coil not within specification.