Monday, May 23, 2011

How to test ASD relay on 2000 jeep grand Cherokee?

Auto Shut Down Relay


Description & Operation



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 and the oxygen sensor heater relay. 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 the ignition key is left in the ON position. This is if the engine has not been running for approximately 1.8 seconds.

Automatic Shutdown (ASD) Sense

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 elements, oxygen sensor heater relay ignition coil and fuel injectors to 12-volt power supply.

This input is used only to sense that the ASD relay is energized. If the Powertrain Control Module (PCM) does not see 12 volts at this input when the ASD should be activated, it will set a Diagnostic Trouble Code (DTC).

Removal & Installation



  1. The ASD relay is located in the Power Distribution Center (PDC). Refer to label on PDC cover for relay location.
  2. Remove PDC cover.
  3. Remove relay from PDC.
  4. Check condition of relay terminals and PDC connector terminals for damage or corrosion. Repair if necessary before installing relay.
  5. Check for pin height (pin height should be the same for all terminals within the PDC connector). Repair if necessary before installing relay.

Testing





Terminal number 30 is connected to battery voltage. For both the ASD and fuel pump relays, terminal 30 is connected to battery voltage at all times.
The PCM grounds the coil side of the relay through terminal number 85.
Terminal number 86 supplies voltage to the coil side of the relay.
When the PCM de-energizes the ASD and fuel pump relays, terminal number 87A connects to terminal 30. This is the OFF position. In the OFF position,
Voltage is not supplied to the rest of the circuit. Terminal 87A is the center terminal on the relay.
When the PCM energizes the ASD and fuel pump relays, terminal 87 connects to terminal 30. This is the ON position. Terminal 87 supplies voltage to the rest of the circuit.

Remove relay from connector before Testing. With the relay removed from the vehicle, use an ohmmeter to check the resistance between terminals 85 and 86. The resistance should be 75 ohms 5 ohms.

Connect the ohmmeter between terminals 30 and 87A. The ohmmeter should show continuity between terminals 30 and 87A.

Connect the ohmmeter between terminals 87 and 30. The ohmmeter should not show continuity at this time.

Connect one end of a jumper wire (16 gauge or smaller) to relay terminal 85. Connect the other end of the jumper wire to the ground side of a 12-volt power source.

Connect one end of another jumper wire (16 gauge or smaller) to the power side of the 12-volt power source. Do not attach the other end of the jumper wire to the relay at this time.


WARNING
Do NOT allow ohmmeter to contact terminals 85 or 86 during this test. Damage to ohmmeter may result.

Attach the other end of the jumper wire to relay terminal 86. This activates the relay. The ohmmeter should now show continuity between relay terminals 87 and 30. The ohmmeter should not show continuity between relay terminals 87A and 30.

Disconnect jumper wires. Replace the relay if it did not pass the continuity and resistance tests. If the relay passed the tests, it operates properly. Check the remainder of the ASD and fuel pump relay circuits.

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.



#30 Common feed
#85 Coil ground
#86 Coil battery
#87 Normally open
#87A Normally closed Type 2 ASD and fuel pump relay

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.

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