Last Modified: 05-13-2024 6.11:8.1.0 Doc ID: RM100000001H986
Model Year Start: 2020 Model: Corolla Prod Date Range: [01/2019 - 09/2022]
Title: HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM (for HV Model): PTC Heater Circuit; 2020 - 2022 MY Corolla Corolla HV [01/2019 - 09/2022]

PTC Heater Circuit

DESCRIPTION

The air conditioning amplifier assembly sends operation signals to the PTC HTR relays when quick heater assembly operation conditions are met. Based on the signals from the air conditioning amplifier assembly, the PTC HTR relays turn on, and power is supplied to the quick heater assembly installed in the air conditioning radiator assembly.

Symptom

Factor

Heating performance is poor when it is cold.

  • Quick heater assembly malfunction
  • Air conditioning amplifier assembly malfunction
  • PTC HTR relay malfunction
  • Harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

INSPECT PTC HTR RELAY

(a) Inspect the PTC HTR relays.

Click here 2020 - 2025 MY Corolla Corolla Hatchback Corolla HV GR Corolla [01/2019 -        ]; HEATING / AIR CONDITIONING: RELAY: ON-VEHICLE INSPECTION

NG

REPLACE PTC HTR RELAY

OK

2.

CHECK HARNESS AND CONNECTOR (POWER SOURCE - PTC HTR RELAY)

(a) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

PTC HTR NO. 1

Tester Connection

Condition

Specified Condition

3 (PTC HTR NO. 1 relay) - Body ground

Power switch off

11 to 14 V

2 (PTC HTR NO. 1 relay) - Body ground

Power switch off

Below 1 V

2 (PTC HTR NO. 1 relay) - Body ground

Power switch on (IG)

11 to 14 V

Standard Voltage:

PTC HTR NO. 2

Tester Connection

Condition

Specified Condition

3 (PTC HTR NO. 2 relay) - Body ground

Power switch off

11 to 14 V

1 (PTC HTR NO. 2 relay) - Body ground

Power switch off

Below 1 V

1 (PTC HTR NO. 2 relay) - Body ground

Power switch on (IG)

11 to 14 V

Standard Voltage:

PTC HTR NO. 3

Tester Connection

Condition

Specified Condition

3 (PTC HTR NO. 3 relay) - Body ground

Power switch off

11 to 14 V

1 (PTC HTR NO. 3 relay) - Body ground

Power switch off

Below 1 V

1 (PTC HTR NO. 3 relay) - Body ground

Power switch on (IG)

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.

CHECK HARNESS AND CONNECTOR (PTC HTR RELAY - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the I48 and I49 air conditioning amplifier assembly connectors.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

PTC HTR NO. 1

Tester Connection

Condition

Specified Condition

1 (PTC HTR NO. 1 relay) - I49-23 (PTC1)

Always

Below 1 Ω

1 (PTC HTR NO. 1 relay) or I49-23 (PTC1) - Body ground

Always

10 kΩ or higher

Standard Resistance:

PTC HTR NO. 2

Tester Connection

Condition

Specified Condition

2 (PTC HTR NO. 2 relay) - I48-16 (PTC2)

Always

Below 1 Ω

2 (PTC HTR NO. 2 relay) or I48-16 (PTC2) - Body ground

Always

10 kΩ or higher

Standard Resistance:

PTC HTR NO. 3

Tester Connection

Condition

Specified Condition

2 (PTC HTR NO. 3 relay) - I48-17 (PTC3)

Always

Below 1 Ω

2 (PTC HTR NO. 3 relay) or I48-17 (PTC3) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

CHECK HARNESS AND CONNECTOR (PTC HTR RELAY - QUICK HEATER ASSEMBLY AND BODY GROUND)

(a) Disconnect the J1 and J2 quick heater assembly connectors.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

PTC HTR NO. 1

Tester Connection

Condition

Specified Condition

5 (PTC HTR NO. 1 relay) - J1-3 (B)

Always

Below 1 Ω

5 (PTC HTR NO. 1 relay) or J1-3 (B) - Other terminals and body ground

Always

10 kΩ or higher

Standard Resistance:

PTC HTR NO. 2

Tester Connection

Condition

Specified Condition

5 (PTC HTR NO. 2 relay) - J1-1 (B)

Always

Below 1 Ω

5 (PTC HTR NO. 2 relay) or J1-1 (B) - Other terminals and body ground

Always

10 kΩ or higher

Standard Resistance:

PTC HTR NO. 3

Tester Connection

Condition

Specified Condition

5 (PTC HTR NO. 3 relay) - J2-2 (B)

Always

Below 1 Ω

5 (PTC HTR NO. 3 relay) or J2-2 (B) - Other terminals and body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.

CHECK HARNESS AND CONNECTOR (QUICK HEATER ASSEMBLY - BODY GROUND)

(a) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

J1-2 (E) - Body ground

Always

Below 1 Ω

J2-1 (E) - Body ground

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

6.

INSPECT QUICK HEATER ASSEMBLY

(a) Remove the quick heater assembly.

Click here 2020 MY Corolla Corolla Hatchback Corolla HV GR Corolla [01/2019 - 03/2019]; HEATING / AIR CONDITIONING: PTC HEATER ASSEMBLY: REMOVAL 2020 - 2022 MY Corolla Corolla Hatchback Corolla HV GR Corolla [03/2019 - 09/2022]; HEATING / AIR CONDITIONING: PTC HEATER ASSEMBLY: REMOVAL

(b) Inspect the quick heater assembly.

Click here 2020 - 2025 MY Corolla Corolla Hatchback Corolla HV GR Corolla [01/2019 -        ]; HEATING / AIR CONDITIONING: PTC HEATER ASSEMBLY: INSPECTION

OK

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

NG

REPLACE QUICK HEATER ASSEMBLY 2020 MY Corolla Corolla Hatchback Corolla HV GR Corolla [01/2019 - 03/2019]; HEATING / AIR CONDITIONING: PTC HEATER ASSEMBLY: REMOVAL 2020 - 2022 MY Corolla Corolla Hatchback Corolla HV GR Corolla [03/2019 - 09/2022]; HEATING / AIR CONDITIONING: PTC HEATER ASSEMBLY: REMOVAL