Refer to Engine Controls Schematic
Power, Ground, VSS, and MIL
.
Circuit Description
The engine controls power relays coil and contacts are connected directly to the battery positive voltage (B+). The engine control module (ECM) controls the relay by grounding the control circuit through an internal solid state device called a driver. When the ECM detects a voltage on the ignition feed circuit, the ECM enables the engine controls power relay. The engine controls power relay controls the switched B+ circuit to the fuel pump relay coil, the fuel injectors, the heated oxygen sensor (HO2S) heaters and the other engine control components that use a switched B+ supply. The ECM also uses the switched B+ circuit to power up a portion of itself, including the circuitry which controls the malfunction indicator lamp (MIL) operation.
Diagnostic Aids
Use the J 35616 connector test adapter kit for any test that requires probing the ECM harness connector or a component harness connector.
Intermittent connections may cause the engine to stall or an intermittent loss of communication. Loss of the switched B+ voltage may cause multiple DTCs to set.
Test for poor connections at the ECM or at the component. Check all other circuits that are spliced to the engine controls power relay for the proper operation. Inspect the harness connectors for intermittent or poor connections. Refer to Testing for Intermittent Conditions and Poor Connections .
Refer to Symptoms or Intermittent Conditions for the Intermittents.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | ||||||||||||||||
2 |
Does the test lamp illuminate on both circuits? | -- | ||||||||||||||||
3 |
Does the test lamp illuminate? | -- | ||||||||||||||||
4 |
Does the test lamp illuminate? | -- | ||||||||||||||||
5 |
Does the test lamp illuminate? | -- | ||||||||||||||||
6 |
Does the current draw measure within the specified range? | 100-200 mA | ||||||||||||||||
7 |
Does the test lamp illuminate on all three circuits? | -- | ||||||||||||||||
8 |
Did you find and repair the condition? | -- | ||||||||||||||||
9 |
Did you find and repair the condition? | -- | ||||||||||||||||
10 | Repair the short to voltage in the engine controls power relay control circuit. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||||||||
11 | Repair the short to ground in the engine controls power relay control circuit. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||||||||
12 | Repair the battery feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||||||||
13 |
Did you find and repair the condition? | -- | ||||||||||||||||
14 | Replace the relay. Is the action complete? | -- | -- | |||||||||||||||
Did you find and repair the condition? | -- | |||||||||||||||||
16 | Inspect the ECM harness connector for a poor connection or poor terminal tension. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and repair the condition? | -- | ||||||||||||||||
17 |
Important: This vehicle is equipped with a theft deterrent system which interfaces with the ECM. Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Did you complete the repair? | -- | -- | |||||||||||||||
18 |
Can communication be established with the ECM? | -- | System OK |
