Engine Coolant Circulation Pump Checking
Engine Coolant Circulation Pump Checking
Observe all safety precautions: => [ Safety Precautions ] Safety Precautions
View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions
Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.
For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.
Special tools, testers and auxiliary items required
• Multimeter
• Wiring diagram.
Test requirements
• The Engine Control Module (ECM) (J623) fuses OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Ignition switched Off.
Theory of Operation
The Engine Coolant Circulation pump is a modular self contained unit. The ECM controls pump operation by sending a trigger voltage to terminal 1 of the pump. Internal circuitry in the pump recognizes this voltage as a command and switches on the pump motor. Battery voltage and ground are the other two inputs to the pump module. The pump is used to circulate coolant through the transmission heat exchanger to preheat the transmission fluid during cold ambient temperatures and will circulate coolant in the engine block after a hot shutdown of the engine in hot ambient temperatures to keep the coolant from boiling. It also is used as a backup pump if the mechanical pump N515 solenoid has a fault.
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check
Start diagnosis
- Disconnect the Engine Coolant Circulation Pump (V178) electrical harness connector.
- Switch the ignition On.
- Using a multimeter, check the Engine Coolant Circulation Pump (V178) electrical harness connector terminals 2 to ground for voltage.
Specified value: Battery voltage
- Using a multimeter, check the Engine Coolant Circulation Pump (V178) electrical harness connector terminal 1 to ground for Resistance.
Specified value: less than 1.5 ohms
- Using a multimeter, check the Engine Coolant Circulation Pump (V178) electrical harness connector terminals 3 to ground for resistance.
Specified value: less than 18 ohms
If the specified values were obtained:
- Replace the Engine Coolant Circulation Pump (V178). Refer to the Repair Information.
If any of the specified values were Not obtained:
Checking signal wire
- Remove the Engine Control Module (ECM) (J623). Refer to appropriate service information.
- Using a multimeter, check the Engine Coolant Circulation Pump (V178) electrical harness connector to the specified component in the chart for resistance.
Specified value: 1.5 ohms Max.
If the specification was Not obtained:
- Check the wiring for a short, high resistance or an open circuit to the specified location in the chart.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring and the resistance check from terminal 3 to the ECM was Not 18 ohms:
- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.
Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.