Circuit Description
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:
| • | ETC FUSE |
| • | O2 SENSOR FUSE |
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 in Engine Electrical.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Power Distribution Schematics in Wiring Systems and Engine Controls Schematics Connector End View References: Power and Grounding Connector End Views , and Electrical Center Identification Views in Wiring Systems, Powertrain Control Module Connector End Views | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 |
Refer to Troubleshooting with a Test Lamp in Wiring Systems. Does the test lamp illuminate on at least one test point of each fuse? | -- | Go to Step 3 | Go to Step 10 | ||||
3 |
Does the test lamp illuminate on either test point of the fuse? | -- | Go to Step 4 | Go to Step 37 | ||||
4 |
Does the test lamp illuminate on either test point of the fuse? | -- | Go to Step 5 | Go to Step 7 | ||||
5 |
Does the test lamp illuminate on either test point of the fuse? | -- | Go to Step 6 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
6 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 34 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
7 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 23 | ||||
8 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 30 | ||||
9 |
Does the test lamp illuminate? | -- | Go to Step 31 | Go to Step 34 | ||||
10 |
Notice: Refer to Test Probe Notice in the Preface section. 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 in Vehicle DTC Information | ||||
12 |
Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 13 | ||||
13 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 18 | ||||
14 |
Does the test lamp illuminate? | -- | Go to Step 15 | Go to Step 30 | ||||
15 |
Does the test lamp illuminate? | -- | Go to Step 32 | Go to Step 34 | ||||
16 |
Does the test lamp illuminate? | -- | Go to Step 17 | Go to Step 30 | ||||
17 |
Does the test lamp illuminate? | -- | Go to Step 32 | Go to Step 34 | ||||
18 |
Does the test lamp illuminate? | -- | Go to Step 19 | Go to Step 34 | ||||
19 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 22 | Go to Step 20 | ||||
20 |
Does the resistance measure greater than the specified value? | 5 ohms | 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 in Wiring Systems. Did you find a condition? | -- | Go to Step 34 | Go to Step 30 | ||||
22 |
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 in Wiring Systems. Does the resistance measure within the specified range? | 70-110 ohms | 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 in Wiring Systems. Does the DMM display the specified value? | ∞ ohms | 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 in Wiring Systems. Does the DMM display the specified value? | ∞ ohms | 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 in Wiring Systems. Does the DMM display the specified value? | ∞ ohms | 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 in Wiring Systems. Does the DMM display the specified value? | ∞ ohms | Go to Step 28 | Go to Step 35 | ||||
28 |
Does the resistance measure more than the specified value? | 3 ohms | 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. Did you complete the repair? | -- | Go to Step 37 | -- | ||||
34 | Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 37 | -- | ||||
35 | Replace the powertrain relay. Refer to Relay Replacement in Wiring Systems. 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 |
Did you correct the condition? | -- | Go to Step 38 | |||||
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 in Vehicle DTC Information | System OK | ||||
