Acura RL. Manual - part 835

ECPS control unit 

The ECPS control unit controls the stepping motor built inside the ECPS valve assy depending on the 
engine speed signal and the vehicle speed signal from the PCM. When a failure occurs, this unit stores a 
DTC and sends a signal to the gauge assembly to turn on the ECPS indicator. 

Fig. 159: ECPS Control Unit - Circuit Diagram 
Courtesy of AMERICAN HONDA MOTOR CO., INC. 

Operation when the vehicle stopped (high assist) 

When the vehicle is stopped, the ECPS control unit closes the ECPS spool valve. When the steering wheel is 
turned, the passage between the increase side power cylinder room and the pump opens at the rotary valve. 
Because the spool valve is closed, all P/S fluid pressure is guided to the increase side power cylinder room 
passing the variable aperture of vehicle moving (A) at the rotary valve. At the same time, the passage 
between the decrease pressure side of the power cylinder room and the reservoir opens at the rotary valve, 
and the P/S fluid inside the decrease side of the power cylinder room returns to the reservoir. By this 
operation, the power steering system assists with strong force depending on the variable aperture of 
stationary steering (B) clearance. 

 

2007 Acura RL 

2005-08 STEERING Steering - RL

  

me 

 

Friday, June 05, 2009 2:20:15 PM

Page 91 

© 2005 Mitchell Repair Information Company, LLC. 

Fig. 160: Electronically Controlled Power Steering System - System Diagram 
Courtesy of AMERICAN HONDA MOTOR CO., INC. 

Operation when the vehicle moving (duty assist) 

The ECPS control unit duty controls the ECPS spool valve depending on the vehicle speed. When the 
steering wheel is rotated, the P/S fluid amount to the increase side of the power cylinder room changes 
depending on the clearance of the variable aperture of stationary steering (A), variable aperture of high 
speed steering (B), and the variable aperture of the ECPS spool valve (C). The assist force is controlled with 
the synthetic valve of these three aperture clearance. Because the synthetic clearance is larger than the 
vehicle in stopped condition, the power steering assist force is controlled lower.

 

2007 Acura RL 

2005-08 STEERING Steering - RL

  

me 

 

Friday, June 05, 2009 2:20:15 PM

Page 92 

© 2005 Mitchell Repair Information Company, LLC. 

Fig. 161: Electronically Controlled Power Steering System - System Diagram 
Courtesy of AMERICAN HONDA MOTOR CO., INC. 

Circuit Diagram 

 

2007 Acura RL 

2005-08 STEERING Steering - RL

  

me 

 

Friday, June 05, 2009 2:20:15 PM

Page 93 

© 2005 Mitchell Repair Information Company, LLC. 

Fig. 162: Electronically Controlled Power Steering System - Circuit Diagram 
Courtesy of AMERICAN HONDA MOTOR CO., INC. 

SYMPTOM TROUBLESHOOTING 

ECPS indicator does not go off after the engine is started 

NOTE:

High engine speed (1,700 RPM or above) when the vehicle is not moving may 
cause the ECPS indicator to come on.

 

2007 Acura RL 

2005-08 STEERING Steering - RL

  

me 

 

Friday, June 05, 2009 2:20:16 PM

Page 94 

© 2005 Mitchell Repair Information Company, LLC.