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HOMESERVICE MANUALSTOYOTA2018PRIUS TWO ECOREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTCOLLISION/AVOIDANCEINTUITIVE PARKING ASSIST SYSTEM - DIAGNOSTICS & CIRCUIT TESTSINTUITIVE PARKING ASSIST SYSTEMDTC C1AEC: FRONT SENSOR COMMUNICATION MALFUNCTION [11/2015 - 12/2018]PROCEDURE

2018 Toyota Prius Two Eco

DTC C1AEC: Front Sensor Communication Malfunction [11/2015 - 12/2018]: Procedure

2018 Toyota Prius Two EcoSECTION Procedure

VEHICLE CONDITION AND WORK DETAILS CHECK

Check the vehicle condition and work details.

Result

Result	Proceed to
The clearance warning ECU assembly or ultrasonic sensor has not been replaced	A
The clearance warning ECU assembly or ultrasonic sensor has been replaced	B

Result:

GO TO CALIBRATION. Refer to CALIBRATION [11/2015 - 12/2018]

Result:

See step 2

CHECK DTC

Check for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Proceed to
NEXT

Result:

See step 3

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 4

CHECK DTC OUTPUT (C1AEC)

Recheck for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [11/2015 - 12/2018]

Result:

See step 5

CHECK CONNECTOR CONNECTION CONDITION (CLEARANCE WARNING ECU ASSEMBLY)

Check that the connector is properly connected to the clearance warning ECU assembly.

Result

Proceed to
NEXT

Result:

See step 6

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 7

CHECK DTC OUTPUT (C1AEC)

Recheck for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (CONNECTOR CONNECTION MALFUNCTION)

Result:

See step 8

CHECK CONNECTOR CONNECTION CONDITION (ULTRASONIC SENSOR)

Check that the connector is properly connected to the front corner ultrasonic sensor and front center ultrasonic sensor.

Result

Proceed to
NEXT

Result:

See step 9

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 10

CHECK DTC OUTPUT (C1AEC)

Recheck for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (CONNECTOR CONNECTION MALFUNCTION)

Result:

See step 11

CHECK HARNESS AND CONNECTOR (CLEARANCE WARNING ECU ASSEMBLY - FRONT CORNER ULTRASONIC SENSOR LH)

Disconnect the F26 clearance warning ECU assembly connector.
Disconnect the B1 front corner ultrasonic sensor LH connector.

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

Standard Resistance

(F26, B1)

(F26)

(B1)

Tester Connection	Condition	Specified Condition
F26-4 (BOF) - B1-4 (BI)	Always	Below 1 Ω
F26-8 (SOF) - B1-5 (SI)	Always	Below 1 Ω
F26-6 (E5) - B1-6 (EI)	Always	Below 1 Ω
F26-4 (BOF) or B1-4 (BI) - Body ground	Always	10 kΩ or higher
F26-8 (SOF) or B1-5 (SI) - Body ground	Always	10 kΩ or higher
F26-6 (E5) or B1-6 (EI) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 12

CHECK HARNESS AND CONNECTOR (FRONT CORNER ULTRASONIC SENSOR LH - FRONT CENTER ULTRASONIC SENSOR LH)

Disconnect the B2 front center ultrasonic sensor LH connector.

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

Standard Resistance

(B1, B2)

(B1)

(B2)

Tester Connection	Condition	Specified Condition
B1-1 (BO) - B2-4 (BI)	Always	Below 1 Ω
B1-2 (SO) - B2-5 (SI)	Always	Below 1 Ω
B1-3 (EO) - B2-6 (EI)	Always	Below 1 Ω
B1-1 (BO) or B2-4 (BI) - Body ground	Always	10 kΩ or higher
B1-2 (SO) or B2-5 (SI) - Body ground	Always	10 kΩ or higher
B1-3 (EO) or B2-6 (EI) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 13

CHECK HARNESS AND CONNECTOR (FRONT CENTER ULTRASONIC SENSOR LH - FRONT CENTER ULTRASONIC SENSOR RH)

Disconnect the B3 front center ultrasonic sensor RH connector.

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

Standard Resistance

(B2, B3)

(B2)

(B3)

Tester Connection	Condition	Specified Condition
B2-1 (BO) - B3-4 (BI)	Always	Below 1 Ω
B2-2 (SO) - B3-5 (SI)	Always	Below 1 Ω
B2-3 (EO) - B3-6 (EI)	Always	Below 1 Ω
B2-1 (BO) or B3-4 (BI) - Body ground	Always	10 kΩ or higher
B2-2 (SO) or B3-5 (SI) - Body ground	Always	10 kΩ or higher
B2-3 (EO) or B3-6 (EI) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 14

CHECK HARNESS AND CONNECTOR (FRONT CENTER ULTRASONIC SENSOR RH - FRONT CORNER ULTRASONIC SENSOR RH)

Disconnect the B4 front corner ultrasonic sensor RH connector.

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

Standard Resistance

(B3, B4)

(B3)

(B4)

Tester Connection	Condition	Specified Condition
B3-1 (BO) - B4-4 (BI)	Always	Below 1 Ω
B3-2 (SO) - B4-5 (SI)	Always	Below 1 Ω
B3-3 (EO) - B4-6 (EI)	Always	Below 1 Ω
B3-1 (BO) or B4-4 (BI) - Body ground	Always	10 kΩ or higher
B3-2 (SO) or B4-5 (SI) - Body ground	Always	10 kΩ or higher
B3-3 (EO) or B4-6 (EI) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 15

REPLACE FRONT CORNER ULTRASONIC SENSOR LH

Replace the front corner ultrasonic sensor LH with a known good one.

HINT:

Refer to REMOVAL [11/2015 - 12/2018]

Result

Proceed to
NEXT

Result:

See step 16

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 17

CHECK DTC (C1AEC)

Check for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (FRONT CORNER ULTRASONIC SENSOR LH WAS DEFECTIVE)

Result:

See step 18

REPLACE FRONT CENTER ULTRASONIC SENSOR LH

Replace the front center ultrasonic sensor LH with a known good one.

HINT:

Refer to REMOVAL [11/2015 - 12/2018]

Result

Proceed to
NEXT

Result:

See step 19

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 20

CHECK DTC (C1AEC)

Check for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (FRONT CENTER ULTRASONIC SENSOR LH WAS DEFECTIVE)

Result:

See step 21

REPLACE FRONT CENTER ULTRASONIC SENSOR RH

Replace the front center ultrasonic sensor RH with a known good one.

HINT:

Refer to REMOVAL [11/2015 - 12/2018]

Result

Proceed to
NEXT

Result:

See step 22

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 23

CHECK DTC (C1AEC)

Check for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (FRONT CENTER ULTRASONIC SENSOR RH WAS DEFECTIVE)

Result:

See step 24

REPLACE FRONT CORNER ULTRASONIC SENSOR RH

Replace the front corner ultrasonic sensor RH with a known good one.

HINT:

Refer to REMOVAL [11/2015 - 12/2018]

Result

Proceed to
NEXT

Result:

See step 25

CLEAR DTC

Clear the DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Clear DTCs

Result

Proceed to
NEXT

Result:

See step 26

CHECK DTC (C1AEC)

Check for DTCs.

Body Electrical > IPA/ICS/Clearance Sonar > Trouble Codes

Result

Result	Proceed to
C1AEC is not output	A
C1AEC is output	B

Result:

END (FRONT CORNER ULTRASONIC SENSOR RH WAS DEFECTIVE)

Result:

REPLACE CLEARANCE WARNING ECU ASSEMBLY. Refer to REMOVAL [11/2015 - 12/2018]

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.