Electronic Power Steering (eps) System Acura ZDX I

Scheme 1

Symptom Troubleshooting Index

System Outline

This vehicle is equipped with an Electronically Controlled Power Steering System (ECPS) with integrated dynamics system. Depending on the vehicle speed, the ECPS control unit controls the ECPS valve. The ECPS valve changes the power steering fluid pressure of the pressure side of the power cylinder. By controlling the power steering fluid pressure electrically, it made it possible to supply stable power steering fluid pressure to the power cylinder which ensures that the steering feel is not influenced by the fluctuation of the engine's speed, and corresponds to the driving situation. The ECPS also has two power assist control maps (sport and comfort). The control maps or "modes" are changed by the Integrated Dynamics System switch. Each mode is different and optimizes the assisting force for that mode.

Scheme 2

Flow Control Valve

This valve stabilizes the power steering fluid pressure of the power steering pump output.

ECPS Valve Assembly

The ECPS valve assembly has a built in spool valve that is operated by the valve motor which is controlled by the ECPS control unit. The spool valve changes the power steering fluid pressure to the power cylinder. When this valve closes, the pressure to the power cylinder increases.

Valve Body Unit

The valve body unit has a built in rotary valve that is driven by the rotation of the steering wheel pinion shaft. This changes the fluid passage between the power steering pump side, power cylinder side, reservoir side, and the ECPS valve side.

Kickback Valve

When kickback occurs from the steering rack, the kickback valve in the feed port decreases the kickback to the steering wheel.

VFV (Variable Force Control Valve)

The valve lessens rapid power steering fluid pressure change.

ECPS Control Unit

The ECPS control unit drives the valve motor built inside the ECPS valve assembly depending on the engine speed signal, the vehicle speed signal from the PCM active damper system indicator from the gauge control module, and integrated dynamics system switch position. When a failure occurs, this unit stores a DTC and sends a signal to the gauge control module to turn on the ECPS indicator.

Scheme 3

Two Power Assist Control Maps

The ECPS has two power assist control maps (sport and comfort). The control maps or "modes" are changed by the Integrated Dynamics System switch. Comfort mode provides a higher assisting force to improve comfort and ease of steering. Sport mode provides a lower assisting force to improve control and handling. The assisting force for each mode is set individually according to the vehicle speed.

Scheme 4

Operation when the vehicle is slow or stopped (high assist)

When the vehicle is moving slowly (such as in a parking lot) or when stopped, the ECPS control unit turns off the valve motor causing the ECPS spool valve to close the port (A) to the reservoir. This creates high pressure at the rotary valve. When the steering wheel turns the pinion shaft, the rotary valve opens the variable ports (B and C) between the pump and the increased pressure side of the steering rack. At the same time, the rotary valve opens passages on the decreased pressure side of the steering rack allowing the power steering fluid to return to the reservoir. By this operation, the power steering system can create strong or full assist in the direction the steering wheel is turned.

Scheme 5

Operation when the vehicle is moving (variable assist)

When the vehicle is moving, the ECPS control unit drives the valve motor speed according to the vehicle speed. The valve motor controls the ECPS spool valve which opens a variable port (A) to the reservoir varying the amount of pressure applied to the rotary valve. When the steering wheel turns the pinion shaft, the rotary valve opens the variable ports (B and C) to the increased pressure side of the steering rack. The amount of steering assist depends on the amount the variable ports are opened or closed at the ECPS spool valve and the rotary valve. Because of these variable clearances, the power steering assist is lower while driving than when the vehicle is stopped.

The Integrated Dynamics System switch controls the mapping or "modes" for the ECPS control unit. These modes (comfort and sport) are selectable by the driver depending on what type of power steering assist is desired. Comfort mode provides a higher assist (lower steering effort required), and sport mode provides a lower assist (higher steering effort required).

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ECPS indicator does not go off after the engine is started

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

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1. Check the active damper system indicator for several seconds when the engine start/stop button is pressed to select the ON mode. Does the indicator come on then go off? YES -Go to step 2. NO -Troubleshoot the active damper system first (see «SYMPTOM TROUBLESHOOTING INDEX»(/acura/zdx/i-2009-2013/remont/wheel-tire-system/#active-damper-system__symptom-troubleshooting-index) ).
2. Operate the integrated dynamics system switch to COMFORT mode.
3. Start the engine, and wait 2 seconds.
4. Check the ECPS indicator for several seconds. Does the indicator come on with the engine running? YES -Go to step 5. NO -Go to step 9 .
5. Press the engine start/stop button to select the OFF mode.
6. Operate the integrated dynamics system switch to SPORT mode.
7. Start the engine, and wait 2 seconds.
8. Check the ECPS indicator for several seconds. Does the indicator come on with the engine running? YES -Go to step 11 . NO -Go to «SYMPTOM TROUBLESHOOTING»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) .
9. Operate the integrated dynamics system switch to SPORT mode.
10. Wait 2 seconds, and check the ECPS indicator for several seconds. Does the indicator come on with the engine running? YES -Go to «SYMPTOM TROUBLESHOOTING»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) . NO -Intermittent failure, the system is OK at this time.
11. Press the engine start/stop button to select the OFF mode.
12. Check the No. 2 (7.5 A) fuse in the driver's under-dash fuse/relay box. Is the fuse blown? YES -Replace the fuse. Press the engine start/stop button to select the ON mode, then select the OFF mode. If the fuse blows again, repair the short to ground on the No. 2 (7.5 A) fuse circuit. NO -Reinstall the checked fuse, then go to step 13.
13. Disconnect the ECPS control unit 12P connector.
14. Press the engine start/stop button to select the ON mode.
15. Measure the voltage between the ECPS control unit 12P connector terminal No. 7 and body ground. Is there battery voltage? YES -Go to step 16. NO -Repair an open in the wire between the ECPS control unit and driver's under-dash fuse/relay box.
16. Press the engine start/stop button to select the OFF mode.
17. Check for continuity between the ECPS control unit 12P connector terminal No. 9 and body ground. Is there continuity? YES -Go to step 18. NO -Repair an open in the wire between the ECPS control unit and body ground (G303).
18. Start the engine.
19. Measure the voltage between the ECPS control unit 12P connector terminal No. 4 and body ground. Is the voltage between 2.1 and 10.6 V? YES -Go to step 28 . NO -Go to step 20.
20. Press the engine start/stop button to select the OFF mode.
21. Measure the resistance between the ECPS control unit 12P connector terminal No. 4 and body ground. Is there 1 Mohms or more? YES -Go to step 22. NO -Go to step 25 .
22. Short the SCS line with the HDS.
23. Disconnect the PCM connector A (49P).
24. Check for continuity between ECPS control unit 12P connector terminal No. 4 and PCM connector A (49P) terminal No. 33. Is there continuity? YES -Replace the PCM (see «PCM REPLACEMENT»(/acura/zdx/i-2009-2013/remont/testing-diagnostics/#pgm-fi-system__pcm-replacement) ). NO -Repair an open in the wire between the ECPS control unit and PCM.
25. Short the SCS line with the HDS.
26. Disconnect the PCM connector A (49P).
27. Measure the resistance between the ECPS control unit 12P connector terminal No. 4 and body ground. Is there 1 Mohms or more? YES -Replace the PCM (see «PCM REPLACEMENT»(/acura/zdx/i-2009-2013/remont/testing-diagnostics/#pgm-fi-system__pcm-replacement) ). NO -Repair a short to body ground in the wire between the ECPS control unit and PCM.
28. Measure the resistance between ECPS control unit 12P connector terminals No. 2 and No. 5, No. 6, No. 11, and No. 12 individually. Is the resistance between 19.8 to 24.2 ohms at 68°F (20°C)? YES -Go to step 29. NO -Go to step 30 .
29. Measure the resistance between ECPS control unit 12P connector terminal No. 2 and body ground. Is there 1 Mohms or more? YES -Go to step 35 . NO -Go to step 32 .
30. Disconnect the ECPS valve motor 6P connector.
31. Measure the resistance between ECPS valve motor 6P connector terminals No. 4 and No. 1, No. 2, No. 5, and No. 6 individually. Is the resistance between 19.8 ohms to 24.2 ohms at 68°F (20°C)? YES -Repair an open in the wire between the ECPS control unit and ECPS valve motor. NO -Replace the valve body unit (see step 15 on «STEERING GEARBOX OVERHAUL»(/acura/zdx/i-2009-2013/remont/manual-power-steering/#hydraulic-power-steering-components) ).
32. Disconnect the ECPS valve motor 6P connector.
33. Measure the resistance between ECPS valve motor 6P connector terminal No. 4 and body ground. Is there 1 Mohms or more? YES -Repair a short to body ground in the wire between the ECPS control unit and ECPS valve motor. NO -Replace the valve body unit (see step 15 on «STEERING GEARBOX OVERHAUL»(/acura/zdx/i-2009-2013/remont/manual-power-steering/#hydraulic-power-steering-components) ).
34. Press the engine start/stop button to Select the ON mode.
35. Measure the voltage between ECPS control unit 12P connector terminal No. 8 and body ground. Is there about 4.5 V or more? YES -Go to step 36. NO -Go to step 37 .
36. Connect ECPS control unit 12P connector terminal No. 8 and body ground with a jumper wire. Does the ECPS indicator go off? YES -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Replace the gauge control module (see «GAUGE CONTROL MODULE REPLACEMENT»(/acura/zdx/i-2009-2013/remont/gauges-instrument-panels/#gauges__gauge-control-module-replacement) ).
37. Press the engine start/stop button to select the OFF mode.
38. Disconnect the gauge control module connector A (32P).
39. Check for continuity between ECPS control unit 12P connector terminal No. 8 and gauge control module connector A (32P) terminal No. 5. Is there continuity? YES -Replace the gauge control module (see «GAUGE CONTROL MODULE REPLACEMENT»(/acura/zdx/i-2009-2013/remont/gauges-instrument-panels/#gauges__gauge-control-module-replacement) ). NO -Repair an open in the wire between the ECPS control unit and gauge control module.

ECPS indicator comes on while driving the vehicle (but the ECPS indicator goes off after the engine is restarted)

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

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1. Start the engine.
2. Check the ECPS indicator. Does the indicator come on with the engine running? YES -Go to «SYMPTOM TROUBLESHOOTING»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) . NO -Go to step 3.
3. Test-drive under these conditions: Drive the vehicle at 6 mph (10 km/h) or more for 3 minutes Engine speed about 2, 100 rpm or more Does the indicator come on? YES -Go to step 4. NO -Intermittent failure, the system is OK at this time.
4. Press the engine start/stop button to select the OFF mode.
5. Disconnect the ECPS control unit 12P connector.
6. Disconnect the navigation control unit connector B (24P).
7. Short the SCS line with the HDS.
8. Disconnect the PCM connector A (49P).
9. Measure the resistance between ECPS control unit 12P connector terminal No. 1 and body ground. Is there 1 Mohms or more? YES -Go to step 10. NO -Repair a short to body ground in the wire between the ECPS control unit and PCM.
10. Check for continuity between ECPS control unit 12P connector terminal No. 1 and PCM connector A (49P) terminal No. 30. Is there continuity? YES -Go to step 11. NO -Repair an open in the wire between the ECPS control unit and the PCM.
11. Substitute a known-good ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ).
12. Reconnect all disconnected connectors.
13. Test drive the vehicle under these conditions: Drive the vehicle at 6 mph (10 km/h) or more for 3 minutes Engine speed about 2, 100 rpm or more Does the indicator come on? YES -Replace the PCM (see «PCM REPLACEMENT»(/acura/zdx/i-2009-2013/remont/testing-diagnostics/#pgm-fi-system__pcm-replacement) ). NO -Replace the original ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ).

Scheme 23

1. Press the engine start/stop button to select the ON mode.
2. Check the ECPS indicator. Does the indicator come on? YES -Intermittent failure, the system is OK at this time. NO -Go to step 3.
3. Press the engine start/stop button to select the OFF mode.
4. Disconnect the ECPS control unit 12P connector.
5. Press the engine start/stop button to select the ON mode.
6. Check the ECPS indicator. Does the indicator come on? YES -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Go to step 7.
7. Press the engine start/stop button to select the OFF mode.
8. Disconnect the gauge control module connector A (32P).
9. Measure the resistance between the ECPS control unit 12P connector terminal No. 8 and body ground. Is there 1 Mohms or more? YES -Replace the gauge control module (see «GAUGE CONTROL MODULE REPLACEMENT»(/acura/zdx/i-2009-2013/remont/gauges-instrument-panels/#gauges__gauge-control-module-replacement) ). NO -Repair a short to body ground in the wire between the ECPS control unit and gauge control module.

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1. Operate the integrated dynamics system switch to COMFORT mode.
2. Start the engine, and wait 2 seconds.
3. Check the ECPS indicator for several seconds. Does the indicator come on with the engine running? YES -Go to step 4. NO -Intermittent failure, the system is OK at this time.
4. Measure the voltage between gauge control module connector B (20P) terminal No. 7 and body ground. Is there battery voltage? YES -Go to step 5. NO -Repair an open in the wire between the integrated dynamics system switch and the gauge control module.
5. Measure the voltage between gauge control module connector B (20P) terminal No. 10 and body ground. Is there battery voltage? YES -Go to step 6. NO -Go to step 11 .
6. Press the engine start/stop button to select the OFF mode.
7. Disconnect the ECPS control unit 12P connector.
8. Press the engine start/stop button to select the ON mode.
9. Measure the voltage between ECPS control unit 12P connector terminal No. 3 and body ground. Is there battery voltage? YES -Go to step 10. NO -Repair an open in the wire between the integrated dynamics system switch and the ECPS control unit.
10. Measure the voltage between ECPS control unit 12P connector terminal No. 10 and body ground. Is there battery voltage? YES -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Repair an open in the wire between the ECPS control unit and the gauge control module.
11. Press the engine start/stop button to select the OFF mode.
12. Disconnect the ECPS control unit 12P connector.
13. Press the engine start/stop button to select the ON mode.
14. Measure the voltage between the gauge control module connector B (20P) terminal No. 10 and body ground. Is there battery voltage? YES -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Go to step 15.
15. Press the engine start/stop button to select the OFF mode.
16. Disconnect the gauge control module connector B (20P).
17. Measure the resistance between the gauge control module connector B (20P) terminal No. 10 and body ground. Is there 1 Mohms or more? YES -Replace the gauge control module (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Repair a short to body ground in the wire between the ECPS control unit and the gauge control module.

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1. Operate the integrated dynamics system switch to SPORT mode.
2. Start the engine, and wait 2 seconds.
3. Check the ECPS indicator for several seconds. Does the indicator come on with the engine running? YES -Go to step 4. NO -Intermittent failure, the system is OK at this time.
4. Press the engine start/stop button to select the OFF mode.
5. Disconnect the ECPS control unit 12P connector.
6. Press the engine start/stop button to select the ON mode.
7. Measure the voltage between ECPS control unit 12P connector terminal No. 10 and body ground. Is there 8 V or less? YES -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ). NO -Go to step 8.
8. Press the engine start/stop button to select the OFF mode.
9. Disconnect the gauge control module connector B (20P).
10. Press the engine start/stop button to select the ON mode.
11. Measure the voltage between ECPS control unit 12P connector terminal No. 10 and body ground. Is there 8 V or less? YES -Replace the gauge control module (see «GAUGE CONTROL MODULE REPLACEMENT»(/acura/zdx/i-2009-2013/remont/gauges-instrument-panels/#gauges__gauge-control-module-replacement) ). NO -Repair a short to power in the wire between the ECPS control unit and the gauge control module.

ECPS indicator does not come on, but there is no power assist

1. Hard steering
2. Uneven or rough steering

1. Press the engine start/stop button to select the ON mode. Is there a clicking noise from the ECPS valve for 2 to 3 seconds? YES -The ECPS system is OK at this time. Go to Symptom Troubleshooting (see «SYMPTOM TROUBLESHOOTING»(/acura/zdx/i-2009-2013/remont/manual-power-steering/#hydraulic-power-steering-components) ). NO -Replace the ECPS control unit (see «ECPS CONTROL UNIT REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/electronic-steering/#electronic-power-steering-eps-system) ) or the valve body unit (see step 15 on «STEERING GEARBOX OVERHAUL»(/acura/zdx/i-2009-2013/remont/manual-power-steering/#hydraulic-power-steering-components) ).

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1. Remove the driver's dashboard undercover (see «DRIVER'S DASHBOARD UNDERCOVER REMOVAL/INSTALLATION»(/acura/zdx/i-2009-2013/remont/gauges-instrument-panels/#dashboard) ).
2. Remove the driver's front door sill trim (see step 1 on «FRONT DOOR SILL AREA»(/acura/zdx/i-2009-2013/remont/exteriorinterior-trim/#interior-trim__front-door-sill-area) ).
3. Remove the driver's kick panel (see step 3 on «FRONT DOOR SILL AREA»(/acura/zdx/i-2009-2013/remont/exteriorinterior-trim/#interior-trim__front-door-sill-area) ).
4. Disconnect the connector (A) from the ECPS control unit (B), then remove the control unit.
5. Install the ECPS control unit in the reverse order of removal.

See also:
• INTEGRATED DYNAMICS SYSTEM SWITCH DOES NOT WORK (INTEGRATED DYNAMICS SYSTEM MODE CANNOT BE SELECTED)
• SYMPTOM TROUBLESHOOTING INDEX
• PCM REPLACEMENT
• STEERING GEARBOX OVERHAUL
• GAUGE CONTROL MODULE REPLACEMENT
• DRIVER'S DASHBOARD UNDERCOVER REMOVAL/INSTALLATION
• FRONT DOOR SILL AREA
• ECPS INDICATOR DOES NOT GO OFF AFTER THE ENGINE IS STARTED
• ECPS INDICATOR COMES ON WHILE DRIVING THE VEHICLE (BUT THE ECPS INDICATOR GOES OFF AFTER THE ENGINE IS RESTARTED)
• ECPS INDICATOR DOES NOT COME ON
• ECPS INDICATOR DOES NOT COME ON, BUT THERE IS NO POWER ASSIST