| Table 1: | EFI Relay Circuit |
Schematic Reference: Engine Controls Schematics
Circuit Description
There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition switch is in the ON position and the engine is not running. System voltage is applied to the indicator bulb. The Powertrain Control Module (PCM) will control the MIL and turn it ON by providing a path to ground.
Diagnostic Aids
Check EFI F-HTR, IGN and GAUGE fuses for opens and make sure the EFI relay is securely mounted into the fuse and relay box.
If the EFI fuse opens (blows) during cranking, check for a shorted fuel pump/circuit. The EFI relay supplies power to the circuit opening relay which in-turn powers the fuel pump. The circuit opening relay is energized during cranking and when reference pulses are monitored by the PCM.
An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.
Use the following relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.
Relay Cavity Identification | |
|---|---|
Switch Load | |
Switch Power | |
Coil Power | Coil Ground |
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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If other ICA functions are not working correctly check for an open GAUGE fuse or for a lack of power and ground to the ICA.
-
This step checks for an open MIL Control circuit or for an internal PCM failure.
-
If the MIL does NOT illuminate when jumpered to ground, the failure is internal to the ICA.
-
This step checks for an open EFI Relay.
-
This step checks for open PCM ground circuits.
-
A shorted sensor reference voltage circuit may cause a no start and no MIL condition.
Step | Action | Value | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
2 | Attempt to start and idle the engine. Does the engine start? | -- | ||||||
Observe Instrument Cluster Assembly (ICA) operation. Do all other functions of the ICA function normally? | -- | Go to ICA Diagnosis in Instrument Panel, Gages and Console | ||||||
Does the MIL illuminate? | -- | |||||||
Does the MIL illuminate? | -- | Go to ICA Diagnosis in Instrument Panel, Gages and Console | ||||||
6 |
Was a repair necessary? | -- | ||||||
7 |
Does the test lamp illuminate? | -- | ||||||
8 |
Does the test lamp illuminate? | -- | ||||||
9 | Connect the test lamp across the relay coil power and coil ground terminals. Does the test lamp illuminate? | -- | ||||||
Does the engine start? | -- | |||||||
11 |
Does the test lamp illuminate? | -- | ||||||
Probe the PCM ground circuit terminals with a test lamp connected to B+. Does the test lamp illuminate on all terminals? | -- | |||||||
Was a repair necessary? | -- | |||||||
14 | Repair the open in the MIL control circuit. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
15 | Repair the open circuit between the EFI fuse and the EFI Relay. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
16 | Repair the open circuit between the IGN fuse and the EFI Relay. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
17 | Repair the open circuit in the EFI Relay ground circuit. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
18 | Replace the EFI Relay. Is the action complete? | -- | -- | |||||
19 | Repair the open circuit between the EFI Relay and the PCM. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
20 | Repair the open circuits between the PCM and ground. Refer to Wiring Repairs in Wiring System. Is the action complete? | -- | -- | |||||
21 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||
22 | Turn ON the ignition, leaving the engine OFF. Is the MIL illuminated? | -- | ||||||
23 |
Observe the MIL operation. Is the MIL illuminated? | -- | System OK |
