Acura TSX / Honda Accord CL. Manual - part 613

YES: Update the ECM/PCM if it does not have the latest software, or substitute a known-
good ECM/PCM, then recheck (see HOW TO SUBSTITUTE THE ECM/PCM ). If the 
symptom/indication goes away with a known-good ECM/PCM, replace the original 
ECM/PCM.  

NO: Intermittent failure, system is OK at this time.  

DTC P0720: COUNTERSHAFT SPEED SENSOR CIRCUIT MALFUNCTION 

1. Start the engine. Hold the engine speed at 3,000 RPM with no load (in neutral) until the radiator fan 

comes on, then let it idle.  

2. Test-drive several miles.  

3. Check the C SHAFT SPD in the DATA LIST with the HDS. 

Is any vehicle speed indicated? 

YES: Intermittent failure, system is OK at this time. Check for poor connections or loose 
terminals at the countershaft speed sensor and the ECM.  

NO: Go to step 4.  

4. Turn the ignition switch OFF.  

5. Disconnect the countershaft speed sensor 3P connector.  

6. Turn the ignition switch ON (II).  

7. Measure voltage between countershaft speed sensor 3P connector terminal No. 1 and body ground. 

Is there about 5 V? 

YES: Go to step 8.  

NO: Repair open in the wire between the ECM (A21) and the countershaft speed sensor, then 
go to step 18 .  

NOTE:

This DTC only occurs on M/T vehicles.

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE PGM-FI System - TSX

  

 

Fig. 84: Measuring Voltage Between Countershaft Speed Sensor 3P Connector Terminal No. 
1 & Body Ground 

8. Measure voltage between countershaft speed sensor 3P connector terminal No. 2 and body ground. 

Is there about 5 V? 

YES: Go to step 9.  

NO: Go to step 10 .  

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE PGM-FI System - TSX

  

 

Fig. 85: Measuring Voltage Between Countershaft Speed Sensor 3P Connector Terminal No. 
2 & Body Ground 

9. Measure voltage between countershaft speed sensor 3P connector terminals No. 1 and No. 3. 

Is there about 5 V? 

YES: Go to step 15 .  

NO: Repair open in the wire between the countershaft speed sensor and G101, then go to 
step 18 .  

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE PGM-FI System - TSX

  

 

Fig. 86: Measuring Voltage Between Countershaft Speed Sensor 3P Connector Terminals No. 
1 & No. 3 

10. Measure voltage between ECM connector terminal A18 and body ground. 

Is there about 5 V? 

YES: Repair open in the wire between the ECM (A18) and the countershaft speed sensor, 
then go to step 18 .  

NO: Go to step 11.  

 

2004 Acura TSX 

2004 ENGINE PERFORMANCE PGM-FI System - TSX