DTC P0688-1F: ECM/PCM Power Relay Sense Circuit Intermittent [12/2019 - 11/2023]: Procedure

1. Confirm whether the auxiliary battery terminals have been disconnected recently.

   Result

   Result	Proceed to
   Terminals have been disconnected.	A
   Terminals have not been disconnected.	B

Result: 

B 

See step  5

Result: 

A 

See step  2

1. Turn the ignition switch to ON (READY) from off.
2. Confirm that the master warning illuminates.

   Result

   Result	Proceed to
   Master warning illuminates.	A
   Master warning does not illuminate.	B

   NOTE:

   DTC P0688-1F may be stored after disconnecting and reconnecting the auxiliary battery terminals. If this happens, the DTC will not be output if the ignition switch is turned off and then ON (READY) again. In this case, clear the DTCs to complete the inspection.

3. Turn the ignition switch off.

Result: 

B 

END 

Result: 

A 

See step  3

1. Read and record the DTCs and Freeze Frame Data.

   Powertrain > Hybrid Control > Trouble Codes 

2. Clear the DTCs and Freeze Frame Data.

   Powertrain > Hybrid Control > Clear DTCs 

3. Turn the ignition switch off and wait for 2 minutes or more.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  4

1. Check for DTCs.

   Powertrain > Hybrid Control > Trouble Codes 

   Result

   Result	Proceed to
   DTC P0688-1F is output again.	A
   DTCs other than P0688-1F are also output.	B

2. Turn the ignition switch off.

Result: 

B 

GO TO DTC CHART (HYBRID CONTROL SYSTEM). Refer to  DIAGNOSTIC TROUBLE CODE CHART [12/2019 - 09/2020]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [09/2020 - 10/2021]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2021 - 11/2023] 

Result: 

A 

See step  5

1. Check the connection of the auxiliary battery terminal.

   OK

   The terminal is connected securely and there is no contact problem.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CONNECT SECURELY 

Result: 

OK 

See step  6

See step  1

Result

Result: 

NG 

CONNECT SECURELY 

Result: 

OK 

See step  7

1. Remove the IGCT relay from the No. 5 floor relay block and No. 5 floor junction block assembly.
2. Disconnect the A31 and H67 hybrid vehicle control ECU connectors.
3. Measure the resistance according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *1	No. 5 Floor Relay Block and No. 5 Floor Junction Block Assembly	*2	IGCT Relay Holder
   *a	Front view of wire harness connector (to Hybrid Vehicle Control ECU)	-	-

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A31-11 (+B1) - 5 (IGCT relay holder)	Ignition switch off	Below 1 Ω
   H67-1 (+B2) - 5 (IGCT relay holder)	Ignition switch off	Below 1 Ω

4. Reconnect the A31 and H67 hybrid vehicle control ECU connectors.
5. Reinstall the IGCT relay.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  8

1. Check for intermittent problems.

   Refer to CHECK FOR INTERMITTENT PROBLEMS [12/2019 - 11/2023]

   1. Check the connection and terminal contact pressure of the connectors and wire harnesses between the hybrid vehicle control ECU and the No. 5 floor relay block and No. 5 floor junction block assembly.
   2. When the ignition switch is ON (READY), jiggle the connectors and wire harnesses between the hybrid vehicle control ECU and the No. 5 floor relay block and No. 5 floor junction block assembly.

   Result

   Result	Proceed to
   Problem symptom does not recur.	A
   Problem symptom recurs.	B

Result: 

A 

REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

Result: 

B 

REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA