DTC Troubleshooting: P0121 (K20C2) - Honda Civic FC/FK 2016-2021

1.

Problem verification 1:

Problem verification 1

?1.	Turn the vehicle to the ON mode.

?2.	Clear the DTC with the HDS.

?3.

Check the parameter(s) below with the HDS.

Signal	Threshold		Current conditions
Signal	Values	Unit	Values	Unit
TP SENSOR A	Less than 0.38	V

Do the current condition(s) match the threshold?


	YES

The failure is duplicated. Go to step 3.


	NO

Go to step 2.

2.

Problem verification 2:

Problem verification 2

?1.

Check the parameter(s) below with the HDS.

Signal	Threshold		Current conditions
Signal	Values	Unit	Values	Unit
TP SENSOR A	More than 4.50	V

Do the current condition(s) match the threshold?


	YES

The failure is duplicated. Go to step 7.


	NO

Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the throttle body and the PCM. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot.?

3.

Determine possible failure area (THL1 line, others):

Determine possible failure area (THL1 line, others)

?1.

Check for Pending or Confirmed DTCs with the HDS.

DTC Description	Confirmed DTC	Pending DTC
P0121 TP Sensor A Out of Range
P0221 TP Sensor B Out of Range

Are DTC P0121 and P0221 indicated at the same time?


	YES

Go to step 5.


	NO

Go to step 4.

4.

Shorted wire check (THL1 line):

Shorted wire check (THL1 line)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.	Jump the SCS line with the HDS, and wait more than 1 minute.

?3.

Disconnect the following connectors.

PCM connector E (80P)

Throttle body 6P connector

?4.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	PCM connector E (80P): disconnected
	Throttle body 6P connector: disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 6:
Test point 2	Body ground

Is there continuity?


	YES

Repair a short in the THL1 wire between the PCM (E50) and the throttle body.?


	NO

The THL1 wire is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM, then recheck. If DTC P0121 goes away and the PCM was substituted, replace the original PCM.?

5.

Determine possible failure area (throttle body, others):

Determine possible failure area (throttle body, others)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.

Disconnect the following connector.

Throttle body 6P connector

?3.	Turn the vehicle to the ON mode.

?4.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode
	Throttle body 6P connector: disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 5:
Test point 2	Body ground

Is there about 5.0 V?


	YES

Replace the throttle body.?


	NO

Go to step 6.

6.

Open wire check (VCC3(DBW) line):

Open wire check (VCC3(DBW) line)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.	Jump the SCS line with the HDS, and wait more than 1 minute.

?3.

Disconnect the following connector.

PCM connector E (80P)

?4.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Throttle body 6P connector: disconnected
	PCM connector E (80P): disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 5:
Test point 2	PCM connector E (80P) No. 75

Is there continuity?


	YES

The VCC3(DBW) wire is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM, then recheck. If DTC P0121 goes away and the PCM was substituted, replace the original PCM.?


	NO

Repair an open in the VCC3(DBW) wire between the PCM (E75) and the throttle body.?

7.

Determine possible failure area (SG3(DBW) line, others):

Determine possible failure area (SG3(DBW) line, others)

?1.

Check for Pending or Confirmed DTCs with the HDS.

DTC Description	Confirmed DTC	Pending DTC
P0121 TP Sensor A Out of Range
P0221 TP Sensor B Out of Range

Are DTC P0121 and P0221 indicated at the same time?


	YES

Go to step 10.


	NO

Go to step 8.

8.

Determine possible failure area (throttle body, others):

Determine possible failure area (throttle body, others)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.

Disconnect the following connector.

Throttle body 6P connector

?3.	Turn the vehicle to the ON mode.

?4.

Measure the voltage between test points 1 and 2.

Test condition	Vehicle ON mode
	Throttle body 6P connector: disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 6:
Test point 2	Body ground

Is there about 5.0 V?


	YES

Replace the throttle body.?


	NO

Go to step 9.

9.

Open wire check (THL1 line):

Open wire check (THL1 line)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.	Jump the SCS line with the HDS, and wait more than 1 minute.

?3.

Disconnect the following connector.

PCM connector E (80P)

?4.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	Throttle body 6P connector: disconnected
	PCM connector E (80P): disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 6:
Test point 2	PCM connector E (80P) No. 50

Is there continuity?


	YES

The THL1 wire is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM, then recheck. If DTC P0121 goes away and the PCM was substituted, replace the original PCM.?


	NO

Repair an open in the THL1 wire between the PCM (E50) and the throttle body.?

10.

Open wire check (SG3(DBW) line):

Open wire check (SG3(DBW) line)

?1.	Turn the vehicle to the OFF (LOCK) mode.

?2.	Jump the SCS line with the HDS, and wait more than 1 minute.

?3.

Disconnect the following connectors.

PCM connector E (80P)

Throttle body 6P connector

?4.

Check for continuity between test points 1 and 2.

Test condition	Vehicle OFF (LOCK) mode
	PCM connector E (80P): disconnected
	Throttle body 6P connector: disconnected
Test point 1	Throttle body 6P connector (female terminals) No. 3:
Test point 2	PCM connector E (80P) No. 76

Is there continuity?


	YES

The SG3(DBW) wire is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM, then recheck. If DTC P0121 goes away and the PCM was substituted, replace the original PCM.?


	NO

Repair an open in the SG3(DBW) wire between the PCM (E76) and the throttle body.?