Ignition Relay Diagnosis (LDD or LUJ)
Diagnostic Instructions
Circuit/System Description
The powertrain relay, is controlled by the engine control module
(ECM) depending upon input from the ignition switch. Battery
positive voltage is supplied to the relay coil and switch. When the
ignition switch is turned to the ON position, the ECM will provide
ground on the control circuit of the relay using a low side driver.
This will allow voltage through the relay switch contacts to the
components. The ECM monitors the voltage level on the control
circuit of the relay.
Diagnostic Aids
The relay electrical contacts may be pitted or sticking. Replace
the powertrain relay , if gently tapping or wiggling the powertrain
relay causes a change in the relays operation.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
EL 43244 Relay Puller Pliers
For equivalent regional tools, refer to
Special Tools .
Circuit/System Verification
|
Warning:
An electric fan under the hood can start up even
when the engine is not running and can injure you. Keep hands,
clothing and tools away from any underhood electric fan.
|
| 1. |
Cycle the ignition from OFF to
ON. You should hear and feel an audible click from the KR75
Powertrain Relay. Repeat as necessary in order to verify KR75
Powertrain Relay operation. |
| 2. |
Operate the vehicle within the
Conditions for running the DTC to verify the DTC does not reset.
You may also operate the vehicle within the conditions that you
observed from the freeze frame/failure records data. |
Circuit/System Testing
| 1. |
Ignition OFF, disconnect the
KR75 Powertrain Relay. |
| 2. |
Ignition ON, verify a test
lamp illuminates between the KR75 Powertrain Relay coil ignition
voltage circuit terminal 85 and ground. |
| ⇒ |
If the test lamp does not illuminate, repair the
KR75 Powertrain Relay coil ignition voltage circuit for a short to
ground or an open/high resistance. Replace the fuse if
necessary. |
| 3. |
Ignition OFF, connect a test
lamp between the KR75 Powertrain Relay coil control circuit
terminal 86 and the KR75 Powertrain Relay coil ignition voltage
circuit terminal 85. |
| ⇒ |
If the test lamp is always ON, test the KR75
Powertrain Relay control circuit for a short to ground. If the
circuit tests normal, replace the K20 Engine Control Module. |
| 4. |
Ignition ON. The test lamp
should turn ON. |
| ⇒ |
If the test lamp is always OFF, test the KR75
Powertrain Relay ECM control circuit for a short to voltage or an
open/high resistance. If circuit tests normal, replace the K20
Engine Control Module. |
|
Note: The ignition
voltage circuit is between the KR75 Powertrain Relay and the ECM.
The ignition voltage is a feedback circuit.
|
| 5. |
Install a 20 A fused jumper
wire between the KR75 Powertrain Relay switch B+ circuit terminal
30 and the KR75 Powertrain Relay switch ignition voltage circuit
terminal 87. |
| 6. |
Attempt to start the engine.
The engine should start. |
| ⇒ |
If the engine does not start, test the ignition
voltage circuit between the KR75 Powertrain Relay and the K20
Engine Control Module for a short to ground or for an open/high
resistance. If the circuit tests normal, replace the K20 Engine
Control Module. |
| 7. |
If all circuits test normal,
test or replace the KR75 Powertrain Relay. |
Component Testing
Relay Test
| 1. |
Ignition OFF, remove the KR75
Powertrain Relay from the electrical centre with the EL
43244 Relay Puller Pliers . |
| 2. |
Test for 70-110 Ω
between terminals 85 and 86. |
| ⇒ |
If not within the specified range, replace the
KR75 Powertrain Relay. |
| 3. |
Test for infinite resistance
between the following terminals: |
| ⇒ |
If not the specified value, replace the KR75
Powertrain Relay. |
| 4. |
Install a 20 A fused jumper
wire between KR75 Powertrain Relay terminal 85 and 12 V. Install a
jumper wire between KR75 Powertrain Relay terminal 86 and ground.
Test for less than 2 Ω between terminals 30 and 87.
|
| ⇒ |
If greater than the specified range, replace the
KR75 Powertrain Relay. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|
