Pinpoint Tests
Transaxle Cooling
Pinpoint Tests
Pinpoint Test A: MECS Cooling Pump Fault
Refer to Wiring Diagram Set 54 (Fusion/Milan/MKZ, Fusion Hybrid, Milan Hybrid, MKZ Hybrid), Climate Control for schematic and connector information. Diagrams By Number
Normal Operation
The Motor Electronics Cooling System (MECS) pump is electrically driven and controlled by the PCM through the MECS pump relay. The PCM energizes the MECS pump relay by pulling the MECS pump output to ground when the ignition is in the ON position.
This pinpoint test is intended to diagnose the following:
- Battery Junction Box (BJB) fuse 13 (15A)
- BJB fuse 47 (10A)
- MECS coolant pump
- Wiring
- MECS coolant pump relay
PINPOINT TEST A: MECS COOLING PUMP FAULT
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
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A1 CHECK FOR DTCs
- Connect the scan tool.
- Enter the following diagnostic mode on the scan tool: RETRIEVE.
- Carry out the PCM on-demand self test.
- Are DTCs retrieved?
Yes
REFER to Testing and Inspection.
No
GO to A2.
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A2 CHECK BJB FUSE 13 (15A)
- Check fuse: BJB 13 (15A).
- Is the resistance less than 5 ohms?
Yes
GO to A5.
No
GO to A3.
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A3 CHECK THE MECS COOLANT PUMP RELAY POWER SUPPLY CIRCUIT FOR A SHORT TO GROUND
- Disconnect: BJB Fuse 13 (15A).
- Disconnect: BJB Relay 44.
- Disconnect: BJB Relay 42.
- Measure the resistance between the output side of BJB fuse 13 (15A) and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to A4.
No
REPAIR circuit SBB13 (GY/RD) for a short to ground. CONNECT all components. TEST the system for normal operation.
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A4 CHECK THE MECS COOLANT PUMP AND HEATER PUMP POWER SUPPLY CIRCUITS FOR A SHORT TO GROUND
- Disconnect: MECS Coolant Pump C1466.
- Disconnect: Heater Pump Motor C1450.
- Measure the resistance between BJB relay 44 pin 5 circuit CE621 (YE/GY), BJB side and ground.
- Measure the resistance between BJB relay 42 pin 5 circuit CHC01 (BN/YE), BJB side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
The condition that caused BJB fuse 13 (15A) to blow is not present. Inspect the wiring harness for an intermittent condition. Repeat test Steps A3 and A4 while wiggling the vehicle wiring harness and visually checking for damage.
No
REPAIR circuit CE621 (YE/GY) or CHC01 (BN/YE) for a short to ground. CONNECT all components. TEST the system for normal operation.
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A5 CHECK THE MECS COOLANT PUMP RELAY (BJB RELAY 44)
- Carry out the relay component test.
- Is MECS pump relay (BJB relay 44) OK?
Yes
GO to A6.
No
INSTALL a new MECS pump relay (BJB relay 44). TEST the system for normal operation.
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A6 CHECK THE MECS COOLANT PUMP RELAY POWER SUPPLY CIRCUIT FOR AN OPEN
- Measure the resistance between BJB fuse 13 (15A) circuit CE621 (YE/GY), BJB side and BJB relay 44 pin 5 circuit CE621 (YE/GY), BJB side.
- Is the resistance less than 5 ohms?
Yes
GO to A7.
No
REPAIR circuit CE621 (YE/GY) for an open. CONNECT all components. TEST the system for normal operation.
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A7 CHECK THE MECS COOLANT PUMP POWER SUPPLY CIRCUIT FOR AN OPEN
- Measure the resistance between BJB relay 44 pin 5 circuit CE621 (YE/GY), BJB side and MECS coolant pump C1466-2, circuit CE621 (YE/GY).
- Is the resistance less than 5 ohms?
Yes
GO to A8.
No
REPAIR circuit CE621 (YE/GY) for an open. CONNECT all components. TEST the system for normal operation.
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A8 CHECK THE MECS COOLANT PUMP GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between MECS coolant pump 1466-1 circuit GD121 (BK/YE) and ground.
- Is the resistance less than 5 ohms?
Yes
GO to A9.
No
REPAIR circuit GD121 (BK/YE). CONNECT all components. TEST the system for normal operation.
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A9 CHECK BJB FUSE 47 (10A)
- Check fuse: BJB 47 (10A).
- Is the resistance less than 5 ohms?
Yes
GO to A10.
No
REPAIR circuit CBK03 (GY) for a short to ground. CONNECT all components. TEST the system for normal operation.
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A10 CHECK FOR VOLTAGE SUPPLIED TO BJB FUSE 47 (10A)
- Disconnect: BJB Fuse 47 (10A).
- Ignition ON.
- Measure the voltage at the supply side of BJB fuse 47 (10A).
- Is the voltage greater than 10 volts?
Yes
GO to A11.
No
REPAIR circuit CE612 (GY/VT) for an open. CONNECT all components. TEST the system for normal operation.
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A11 CHECK THE MECS COOLANT PUMP RELAY CONTROL POWER SUPPLY CIRCUIT FOR AN OPEN
- Ignition OFF.
- Measure the resistance between the output side of BJB fuse 47 (10A), circuit CBK03 (GY) and BJB relay 44 pin 1 circuit CBK03 (GY).
- Is the resistance less than 5 ohms?
Yes
GO to A12.
No
REPAIR circuit CBK03 (GY) for an open. CONNECT all components. TEST the system for normal operation.
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A12 CHECK FOR GROUND AT THE MECS COOLANT PUMP RELAY
- Connect: BJB fuse 47 (10A).
- Ignition ON.
- Measure the voltage between BJB relay 44 pins 1 and 2, BJB side.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new MECS pump. REFER to Motor Electronics Pump Motor Electronics Pump. CONNECT all components. TEST the system for normal operation.
No
GO to A13.
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A13 CHECK THE MECS COOLANT PUMP RELAY CONTROL GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175T.
- Measure the resistance between BJB relay 44 pin 2, BJB side circuit CE318 (VT) and PCM C175T-49 circuit CE318 (VT).
- Is the resistance less than 5 ohms?
Yes
INSTALL a new PCM. REFER to Electronic Engine Controls - Hybrid Service and Repair.
CONNECT all components. TEST the system for normal operation.
No
REPAIR circuit CE318 (VT) for an open. CONNECT all components. TEST the system for normal operation.
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