Pinpoint Test E: Insufficient, Erratic Or No Heat
- Normal Operation and Fault Conditions
When the engine is at operating temperature hot coolant flows from the engine through the heater core and back to the engine. Correct coolant temperatures are critical for good heater performance.
Possible Sources
- Low engine coolant level
- Plugged or partially plugged heater core
- (If equipped) cabin heater coolant pump
- (If equipped) transmission fluid heater coolant control valve
- (If equipped) cabin heater coolant diverter valve (PHEV)
- Temperature door binding or stuck
- Temperature door actuator
Visual Inspection and Pre-checks
- Inspect for low engine coolant level.
- E1 CHECK FOR CORRECT ENGINE COOLANT LEVEL
- Ignition OFF.
- Check the engine coolant level.
Is the engine coolant at the correct level (hot or cold) as indicated on the engine coolant recovery reservoir?
Yes GO to E3 No GO to E2 - E2 CHECK THE ENGINE COOLING SYSTEM FOR LEAKS
- Pressure test the cooling system for leaks. Refer to the appropriate Engine System article for the procedure.
Does the cooling system leak?
Yes REPAIR the coolant leak. No FILL and BLEED the cooling system. Refer to the appropriate Engine System article for the procedure. After filling and bleeding the cooling system, GO to E3 - E3 CHECK FOR COOLANT FLOW TO THE HEATER CORE
- Run the engine until it reaches normal operating temperature.
- On the HVAC controls, select the FLOOR position, then set the temperature control to full warm and the blower to the lowest setting.
- Using a suitable temperature measuring device, check the temperature of the heater core inlet hose.
Is the heater core inlet hose temperature above 65.5 deg.C (150 deg.F)?
Yes GO to E4 No DIAGNOSE the engine does not reach operating temperature. Refer to the appropriate Engine System article for the procedure. - E4 CHECK FOR A PLUGGED OR RESTRICTED HEATER CORE
- Using a suitable temperature measuring device, measure the temperature of the heater core outlet hose.
Is the heater core outlet hose temperature similar to the inlet hose temperature [within approximately 6-17 deg.C (10-30 deg.F)]?
Yes DIAGNOSE for a temperature door actuator not operating correctly. GO to Pinpoint Test H
GO to Pinpoint Test INo GO to E5 - E5 CHECK FOR A PLUGGED OR RESTRICTED HEATER CORE RETURN LOOP
- INSTALL a temporary bypass hose from the heater core outlet to the thermostat housing assembly (as applicable).
- Using a suitable temperature measuring device, measure the heater core inlet and outlet hose temperatures.
Is the heater core outlet hose temperature similar to the inlet hose temperature [within approximately 6-17 deg.C (10-30 deg.F)]?
Yes There is a restriction in the coolant control valve and/or the hoses. If equipped with a cabin heater coolant pump, DIAGNOSE for the cabin coolant pump causing a possible restriction of flow to the heater core.
Using a suitable temperature measuring device, check the temperature of the coolant hose to the applicable component. If equipped with a transmission fluid heater coolant control valve, or If equipped with a cabin heater coolant diverter valve (PHEV), DIAGNOSE for the coolant control valve causing a possible restriction of flow to the heater core.
Using a suitable temperature measuring device, check the temperature of the coolant hose to the applicable component. REPAIR or replace components as necessary.No INSTALL a new heater core. REFER to: Heater Core . TEST the system for normal operation.