Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5501268
Diagnostic Instructions
Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic
System Check - Vehicle
Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis
An overview of each diagnostic category can be found here: Diagnostic Procedure
Instructions
DTC Descriptor
DTC P2687
Fuel Heater Relay Control Circuit
DTC P2688
Fuel Heater Control Circuit Low
DTC P2689
Fuel Heater Control Circuit High
Diagnostic Fault Information
| Circuit |
Short to Ground |
Open/High Resistance |
Short to Voltage |
Signal Performanc |
| Ignition — Relay Coil |
P2688 |
P2687 |
— |
— |
| B+ — Relay Switch |
* |
*** |
— |
— |
| Control — Component |
* |
*** |
** |
— |
| Control — Relay Coil |
P2688** |
P2687*** |
P2689*** |
— |
| Ground — Component |
— |
*** |
*** |
— |
| * Opens the fuse that supplies voltage to the component. ** Component = Always On *** Component = Always Off |
|
|
|
|
Typical Scan Tool Data
Fuel Heater Control Circuit High Test Status
|
Circuit |
Short to Ground |
Open |
Short to Voltage |
|
|
Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay |
|
|
|
|
|
Ignition — Relay Coil |
Not Run / Okay |
Not Run / Okay |
Not Run / Okay |
|
|
Control — Relay Coil |
Not Run / Okay |
Not Run / Okay |
Malfunction |
|
Fuel Heater Control Circuit Low Test Status
| Circuit |
Short to Ground |
Open |
Short to Voltage |
| Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay |
|
|
|
| Ignition — Relay Coil |
Malfunction |
Not Run / Okay |
Not Run / Okay |
| Control — Relay Coil |
Malfunction |
Not Run / Okay |
Not Run / Okay |
Fuel Heater Control Circuit Open Test Status
| Circuit |
Short to Ground |
Open |
Short to Voltage |
| Operating Conditions: Ignition = On Parameter Normal Range: Not Run / Okay |
|
|
|
| Ignition — Relay Coil |
Not Run / Okay |
Malfunction |
Not Run / Okay |
| Control — Relay Coil |
Not Run / Okay |
Malfunction |
Not Run / Okay |
Circuit/System Description
For an overview of the component/system, refer to: Fuel System Description
| Circuit |
Description |
| Ignition — Relay Coil |
Supplied from a relay. |
| B+ — Relay Switch |
Supplied from a fuse. |
| Control — Component |
The output circuit is switched to 12 V to activate the component. |
| Control — Relay Coil |
The output circuit is switched to ground to activate the component. |
| Ground — Component |
Chassis Ground |
|
Component |
Description |
|
|
K20 Engine Control Module |
The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, |
|
| Component |
Description |
|
interprets the data and adjusts the engine actuators accordingly. |
| KR22 Fuel Heater Relay |
A relay is a switch that is actuated by a solenoid. |
Conditions for Running the DTC
Battery Voltage = Greater than 11 V
Ignition and Start Switch Signal = On or Engine = Running
Frequency the DTC runs = Continuously — After the running conditions are met
Conditions for Setting the DTC
Control Circuit = Commanded state does not match the actual state — For greater than 3 s
Actions Taken When the DTC Sets
DTCs listed in the DTC Descriptor category = Type C DTC
Conditions for Clearing the DTC
DTCs listed in the DTC Descriptor category = Type C DTC
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Master Electrical Component List
Electrical Information Reference
Circuit Testing
Connector Repairs
Electrical Relay Replacement
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
Circuit/System Verification
- Ignition » On / Vehicle » In Service Mode
- Perform the scan tool control function: Fuel Heater Relay » On and Off
Verify the scan tool parameter:
Fuel Heater Control Circuit High Test Status = Not Run or Okay
Fuel Heater Control Circuit Low Test Status = Not Run or Okay
Fuel Heater Control Circuit Open Test Status = Not Run or Okay
⇒ If not the specified state
Refer to: Circuit/System Testing
⇓ If the specified state
- Perform the scan tool control function: Fuel Heater Relay » On and Off
Verify a click can be heard or felt at the following component(s) when the scan tool control
function was commanded: KR22 Fuel Heater Relay
⇒ If a click cannot be heard or felt
Refer to: Circuit/System Testing
⇓ If a click can be heard or felt
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the
vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Verify the DTC does not set.
⇒ If the DTC sets
Refer to: Circuit/System Testing
⇓ If the DTC is not set
- All OK.
Circuit/System Testing
- Ignition/Vehicle & All vehicle systems » Off
- Remove the component: KR22 Fuel Heater Relay
- Ignition » On / Vehicle » In Service Mode
- Verify a test lamp turns On between the test points: Ignition circuit terminal 2 & Ground
⇒ If the test lamp does not turn On and the circuit fuse is OK
4.1. Ignition/Vehicle » Off & Remove » Test lamp
4.2. Test for less than 2 Ω between the test points: Ignition circuit terminal 2 @ Relay Socket
& Output terminal @ F85UA Fuse
⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit.
⇒ If less than 2 Ω » Verify the fuse is OK and there is voltage at the fuse.
⇓ If the test lamp does not turn On and the circuit fuse is open
4.1. Ignition/Vehicle » Off & Remove » Test lamp
4.2. Test for infinite resistance between the test points: Ignition circuit terminal 2 & Ground
⇒ If less than infinite resistance » Repair the short to ground on the circuit.
⇒ If infinite resistance » Replace the component: KR22 Fuel Heater Relay
⇒ If the test lamp turns On
- Verify a test lamp does not turn On between the test points: Control circuit terminal 1 & B+
⇒ If the test lamp turns On
5.1. Ignition/Vehicle » Off & Remove » Test lamp
5.2. Disconnect the electrical connector: X2 @ K20 Engine Control Module
5.3. Test for infinite resistance between the test points: Control circuit terminal 1 @ Relay
Socket & Ground
⇒ If less than infinite resistance » Repair the short to ground on the circuit.
⇒ If infinite resistance » Replace the component: K20 Engine Control Module
⇓ If the test lamp does not turn On
- Remove » Test Lamp
- Perform the scan tool control function: Fuel Heater Relay » On
Verify the scan tool parameter: Fuel Heater Relay Control Circuit High Voltage Test Status =
OK
⇒ If not the specified state
7.1. Ignition/Vehicle » Off
7.2. Disconnect the electrical connector: X2 @ K20 Engine Control Module
7.3. Ignition » On / Vehicle » In Service Mode
7.4. Test for less than 1 V between the test points: Control circuit terminal 1 @ Relay Socket &
Ground
⇒ If 1 V or greater » Repair the short to voltage on the circuit.
⇒ If less than 1 V » Replace the component: K20 Engine Control Module
⇓ If the specified state
- Connect a 3 A fused jumper wire between the test points: Control circuit terminal 1 & Ignition
circuit terminal 2
- Perform the scan tool control function: Fuel Heater Relay » On
Verify the scan tool parameter: Fuel Heater Relay Control Circuit High Voltage Test Status =
Malfunction
⇒ If not the specified state
9.1. Ignition/Vehicle » Off & Remove » Jumper wire(s)
9.2. Disconnect the electrical connector: X2 @ K20 Engine Control Module
9.3. Test for less than 2 Ω between the test points: Control circuit terminal 1 @ Relay Socket &
Terminal 37 @ Control module harness
⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit.
⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module
⇓ If the specified state
- Verify a test lamp turns On between the test points: B+ circuit terminal 3 & Ground
⇒ If the test lamp does not turn On and the circuit fuse is OK
10.1. Ignition/Vehicle » Off & Remove » Test lamp
10.2. Test for less than 2 Ω between the test points: B+ circuit terminal 3 @ Relay Socket &
Output terminal @ F10UB Fuse
⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit.
⇒ If less than 2 Ω » Verify the fuse is OK and there is voltage at the fuse.
⇒ If the test lamp does not turn On and the circuit fuse is open
10.1. Ignition/Vehicle » Off & Remove » Test lamp
10.2. Test for infinite resistance between the test points: B+ circuit terminal 3 & Ground
⇒ If less than infinite resistance » Repair the short to ground on the circuit.
⇓ If infinite resistance
10.3. Disconnect the electrical connector: R29 Fuel Filter
10.4. Test for infinite resistance between the test points: Control circuit terminal 5 @ Relay
Socket & Ground
⇒ If less than infinite resistance » Repair the short to ground on the circuit.
⇓ If infinite resistance
10.5. Replace the component: F10UB Fuse
10.6. Install the component: KR22 Fuel Heater Relay
10.7. Connect a test lamp between the test points: Control circuit terminal 2 & Ground circuit
terminal 1
10.8. Ignition » On / Vehicle » In Service Mode
10.9. Perform the scan tool control function: Fuel Heater Relay » On and Off
Verify the test lamp turns On and Off.
⇒ If the test lamp does not turn On and Off » Test or replace the component: KR22 Fuel
Heater Relay
⇒ If the test lamp turns On and Off » Test or replace the component: R29 Fuel Filter
⇓ If the test lamp turns On
- Ignition/Vehicle & All vehicle systems » Off
- Install the component: KR22 Fuel Heater Relay
- Disconnect the electrical connector: R29 Fuel Filter
- Test for less than 10 Ω between the test points: Ground circuit terminal 1 & Ground
⇒ If 10 Ω or greater
14.1. Disconnect the ground connection: G405
14.2. Test for less than 2 Ω between the test points: Ground circuit terminal 1 @ Component
harness & Terminal G405
⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit.
⇒ If less than 2 Ω » Repair the open/high resistance in the ground connection.
⇓ If less than 10 Ω
- Connect a test lamp between the test points: Control circuit terminal 2 & Ground circuit
terminal 1
- Ignition » On / Vehicle » In Service Mode
- Perform the scan tool control function: Fuel Heater Relay » On and Off
Verify the test lamp turns On and Off.
⇒ If the test lamp is always Off
Repair the open/high resistance in the circuit: Control Circuit
⇒ If the test lamp is always On
Repair the short to voltage on the circuit: Control Circuit
⇓ If the test lamp turns On and Off
- Test or replace the component: R29 Fuel Filter
Component Testing
Relay Test
- Ignition/Vehicle » Off
- Remove the component: KR22 Fuel Heater Relay
- Test for 70 to 110 Ω between the test points: Component terminal 1 & 2
⇒ If not between 70 and 110 Ω
Replace the component: KR22 Fuel Heater Relay
⇓ If between 70 and 110 Ω
- Test for infinite resistance between the test points:
Component terminal 3 & 2
Component terminal 3 & 1
Component terminal 3 & 5
Component terminal 2 & 5
⇒ If less than infinite resistance
Replace the component: KR22 Fuel Heater Relay
⇓ If infinite resistance
- Connect a 3 A fused jumper wire between the test points: Component terminal 1 & 12 V
Connect a jumper wire between the test points: Component terminal 2 & Ground
- Test for less than 2 Ω between the test points: Component terminal 3 & 5
⇒ If 2 Ω or greater
Replace the component: KR22 Fuel Heater Relay
⇓ If less than 2 Ω
- All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair
Verification
Fuel Filter Assembly Replacement — R29 Fuel Filter
Electrical Relay Replacement
For control module replacement, programming, and setup refer to: Control Module
References