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Home >> Isuzu >> 2007 >> i-290 LS, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 86 (Engine Control System & Fuel System - 3.7L - Diagnosis & Troubleshooting) >> Powertrain Relay Diagnosis >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit, via an internal integrated circuit called an output driver module (ODM). When the PCM commands the relay ON, the relay coil creates an electromagnetic field. This electromagnetic field overcomes the spring tension and pulls the armature contact into the stationary contact of the relay load circuit. The closing of the relay contacts allows current to flow from the battery to the following fuses:

When the ignition switch is turned to the OFF position, the powertrain relay will continue to be energized for 5 seconds after the key is turned OFF. Once the power is interrupted to the output driver module in the PCM, the relay electromagnetic field collapses. This allows the spring tension to separate the relay armature contact from the relay load circuit contact, which interrupts current flow to the fuses.

If the powertrain relay fails to close the engine will crank, but will not run. The PCM class 2 communications will be available with the use of a scan tool.

The powertrain relay system diagnosis table assumes that the vehicle battery if fully charged. Refer to Battery Inspection/Test (Non-HP2) .

Powertrain Relay Diagnosis

Step Action Values Yes No
Schematic Reference: Power Distribution Schematics and Engine Controls Schematics
Connector End View References: Master Electrical Component List
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Turn ON the ignition, with the engine OFF.
  2. Remove the underhood fuse block cover.
  3. Probe the following fuses with a test lamp that is connected to a good ground:
    • ETC Fuse
    • O2 SENSOR Fuse
Refer to Troubleshooting with a Test Lamp .Does the test lamp illuminate on at least one test point of each fuse?		 - Go to Step 3  Go to Step 10 
3
  1. Turn OFF the ignition.
  2. Probe both test points of the ETC fuse in the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate on either test point of the fuse?		 - Go to Step 4  Go to Step 37 
4
  1. Turn OFF the ignition.
  2. Remove the powertrain relay from the underhood fuse block with the J 43244  Relay Puller Pliers. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) .
  3. Probe both the test points of the ETC fuse with a test lamp that is connected to a good ground.
Does the test lamp illuminate on either test point of the fuse?		 - Go to Step 5  Go to Step 7 
5
  1. Turn OFF the ignition.
  2. Remove the O2 Sensor fuse from the underhood fuse block.
  3. Probe both test points of the ETC fuse with a test lamp that is connected to a good ground.
Does the test lamp illuminate on either test point of the fuse?		 - Go to Step 6  Go to Diagnostic System Check - Vehicle
6
  1. Turn OFF the ignition.
  2. Remove the ETC fuse from the underhood fuse block.
    3. NOTE: Refer to Test Probe Notice .
  3. Probe the powertrain relay load circuit bus bar terminal in the underhood fuse block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .
Does the test lamp illuminate?		 - Go to Step 34  Go to Diagnostic System Check - Vehicle
7
  1. Turn OFF the ignition.
    2. NOTE: Refer to Test Probe Notice .
  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to battery positive voltage. Refer to Probing Electrical Connectors .
Does the test lamp illuminate?		 - Go to Step 8  Go to Step 23 
8
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) electrical connector that contains the relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp this is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 9  Go to Step 30 
9
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Probe the powertrain relay coil control circuit at the underhood fuse block electrical connector with a test lamp that is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 31  Go to Step 34 
10
  1. Turn OFF the ignition.
  2. Remove the powertrain relay from the underhood fuse block with the J 43244  . Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) .
    3. NOTE: Refer to Test Probe Notice .
  3. Probe the battery positive voltage terminal for the powertrain relay coil in the underhood fuse block with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .
Does the test lamp illuminate?		 - Go to Step 12  Go to Step 11 
11 Probe the mounting stud for the positive battery cable at the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 34  Go to Diagnostic System Check - Vehicle
12
  1. Turn OFF the ignition.
  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 16  Go to Step 13 
13
  1. Turn ON the ignition, with the engine OFF.
  2. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 14  Go to Step 18 
14
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connector that contains the relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the powertrain relay coil control circuit at the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 15  Go to Step 30 
15
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Disconnect the powertrain relay coil connector circuit terminal from the underhood fuse block electrical connector. Refer to Delphi Connectors (Micro.64) or Delphi Connectors (Micro-Pack 100W) or Delphi Connectors (Pull To Seat) or Delphi Connectors (Push To Seat) or Delphi Connectors (Weather Pack) or Delphi Connectors (12-Way) .
  5. Connect the electrical connector that contained the powertrain relay coil control circuit to the underhood fuse block.
  6. Connect the negative battery cable at the battery.
  7. Turn ON the ignition, with the engine OFF.
  8. Probe the powertrain relay coil control circuit terminal at the underhood fuse block electrical connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 32  Go to Step 34 
16
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit. Refer to Powertrain Control Module Replacement .
  3. Probe the powertrain relay coil control circuit terminal in the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 17  Go to Step 30 
17
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Connect the negative battery cable at the battery.
  5. Probe the powertrain relay coil connector circuit at the underhood fuse block electrical connector with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 32  Go to Step 34 
18
  1. Turn OFF the ignition.
  2. Probe the battery positive voltage terminal for the powertrain relay armature at the underhood fuse block with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 19  Go to Step 34 
19
  1. Turn ON the ignition, with the engine OFF.
    2. NOTE: Refer to Test Probe Notice .
  2. Probe the powertrain relay coil control circuit terminal at the underhood fuse block with a test lamp that is connected to battery positive voltage.
Does the test lamp illuminate?		 - Go to Step 22  Go to Step 20 
20
  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the powertrain relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Disconnect the PCM electrical connector that contains the powertrain relay coil control circuit. Refer to Powertrain Control Module Replacement .
  5. Measure the resistance of the powertrain relay coil control circuit from the underhood fuse block electrical connector to the PCM electrical connector with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the resistance measure greater than the specified value?		 5 Ω Go to Step 33  Go to Step 21 
21 Test the powertrain relay coil control bus bar circuit of the underhood fuse block for a high resistance or an open. Refer to Circuit Testing .
Did you find a condition?		 - Go to Step 34  Go to Step 30 
22
  1. Turn OFF the ignition.
  2. Connect a 20-amp fused jumper wire between the battery positive voltage circuit terminal of the underhood fuse block and the relay load circuit terminal of the underhood fuse block. Refer to Using Fused Jumper Wires .
  3. Probe the following fuses with a test lamp that is connected to a good ground:
    • ETC fuse
    • O2 SENSOR fuse
Does the test lamp illuminate on at least one test point of each fuse?		 - Go to Step 23  Go to Step 34 
23 Measure the resistance from terminal #85 of the relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the resistance measure within the specified range?		 70-110 Ω Go to Step 24  Go to Step 35 
24 Measure the resistance from terminal #30 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the DMM display the specified value?		 ∞ Ω Go to Step 25  Go to Step 35 
25 Measure the resistance from terminal #30 of the relay to terminal #85 with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the DMM display the specified value?		 ∞ Ω Go to Step 26  Go to Step 35 
26 Measure the resistance from terminal #85 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the DMM display the specified value?		 ∞ Ω Go to Step 27  Go to Step 35 
27 Measure the resistance from terminal #86 of the relay to terminal #87 with a DMM. Refer to Troubleshooting with a Digital Multimeter .
Does the DMM display the specified value?		 ∞ Ω Go to Step 28  Go to Step 35 
28
  1. Connect a 20-amp fused jumper wire from the battery positive cable at the battery to relay terminal #85. Refer to Using Fused Jumper Wires .
  2. Connect a jumper wire from the negative battery cable to the relay terminal #86.
  3. Measure the resistance from terminal #30 of the relay to terminal #87 with a DMM.
Does the resistance measure more than the specified value?		 3 Ω Go to Step 35  Go to Step 29 
29 Test for an intermittent and for a poor connection at the powertrain relay location on the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections .
Did you find a condition?		 - Go to Step 34  Go to Intermittent Conditions 
30 Test for shorted terminals and poor connections at the PCM electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 37  Go to Step 36 
31 Repair the short to ground in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 37  -
32 Repair the short to voltage in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 37  -
33 Repair the high resistance or an open in the relay coil control circuit between the underhood fuse block and the PCM. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 37  -
34 Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement .
Did you complete the replacement?		 - Go to Step 37  -
35 Replace the powertrain relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) .
Did you complete the replacement?		 - Go to Step 37  -
36 Replace the PCM. Refer to Powertrain Control Module Replacement .
Did you complete the replacement?		 - Go to Step 37  -
37
  1. Reassemble the vehicle as necessary.
  2. Replace any open fuses.
  3. Clear any DTCs with a scan tool.
  4. Start the engine.
  5. Operate the vehicle in order to verify the repair.
Did you correct the condition?		 - Go to Step 38  Go to Engine Cranks but Does Not Run 
38 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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