DodgeRam.info Please visit Geno's Garage for truck accessories
	Fault Code 42 - Auto shutdown relay circuit
	OBD1 DTC's for 1994-1997 Rams with Gas Engines
	.

Code 42 indicates a problem with the auto shutdown relay circuit. It is intended to indicate a bad connection on the ASD relay.

In general, if there is no complaint about engine stalling, this code may not be important. The computer will set this fault if it detects a sudden change in frequency from the engine speed sensor, crankshaft position sensor, and/or camshaft position sensor. If someone revs the engine and then pops the clutch too suddenly the computer may set 42 as a response to a near stall.

There are four wires running to the ASD relay:

• Pin 30 - (depends on year) Gray/White or Red/Light Blue
  • +12V from Fuse 4 or Fuse 6
  • should read +12V all of the time
• Pin 87 - Dark Green/Orange
  • ASD Relay output from the PCM control
  • This lead controls power to the generator field, fuel injectors, and oxygen sensor heaters.
• Pin 86 - Light Green/Black
  • Start/Run feed from the ignition switch and Fuse 9
  • should read +12V when the ignition switch is ON
  • Should read 0V when the ignition switch is OFF
• Pin 85 - Dark Blue/Yellow:   ASD control from PCM
  • The computer uses this line to switch the relay.

TERMINAL LEGEND
NUMBER	IDENTIFICATION
30	Common Feed
85	Coil Ground
86	Coil Battery
87	Normally Open
87A	Normally Closed

 

Diagnosis procedure:

First - unplug the relay and check socket pins 30 and 86 for correct voltages. If there is a problem, check the fuse feeding the pin. If the fuse is OK, use an ohm meter to check for a broken wire between the fuse and the relay.

Second - Unplug the relay and use and ohm meter to verify that the relay coil resistance is 75 ± 5 ohms by looking measuring between pins 85 and 86 on the relay. If the circuit is open or the resistance is too high, the relay coil is blown. If the resistance is too low, the coil is shorted. Replace the relay if the coil resistance in not within tolerance.

Third - remove the relay and look at the base terminals.

• Measure the continuity from relay pin 87A to relay pin 30. It should read a very low resistance.
• Measure between pins 87 and 30; this should be an open circuit.
• Connect a jumper wire from pin 85 to ground. Connect a jumper wire from pin 86 to +12V
  • Measure the continuity between pin 30 and pin 87; it should be a low resistance
  • Measure the continuity between pins 30 and 87a; it should be a on open circuit
• If these measurements are not correct, the relay is stuck and should be replaced.

Fourth - Use an ohm meter to probe the Dark Blue/Yellow from Pin 85 to the terminal on the computer (see the service manual for the proper pin). The should be a very low resistance between the probes. If it is not, the wire is open. If the wire seems OK, wiggle the wire in several places to see if there is an intermittent connection.

Fifth - With the relay installed, turn on the ignition and probe the Dark Blue/Yellow at the computer. This wire should be at 0 volts. If it is not, suspect a computer problem.

Sixth - With the relay installed, turn on the ignition and probe the Light Green/Black wire at the computer (see the service manual for the proper pin). This wire should be at +12 volts. If it is not, replace the relay and check again. If it is still not reading +12 V, suspect a wiring break between the relay and the computer. NOTE: An intermittent problem with this wire or with the relay contacts may not set a fault code, but it will cause problems such as: stalling, under charging the battery, rough idle, stumble.