Initial Inspection and Diagnostic Overview
How to Troubleshoot the EPS
EPS Indicator
Under normal conditions, the EPS indicator (A) comes on when the ignition switch is turned to ON (II), then goes off after the engine is started. This indicates that the bulb and its circuit are operating correctly.
If there is a failure in the system after the engine is started, the EPS indicator will stay on, and the power assist is turned off or restricted.
When the EPS indicator comes on, the control unit memorizes the DTC. In this case, the control unit will not activate the EPS system after the engine starts again, but it keeps the EPS indicator on.
When DTC 11, 12, or 13 is stored in the control unit, the EPS indicator will stay on until the DTC is erased. Even though the system is operating normally, the EPS indicator will come on under the following conditions:
- When the vehicle is barely moving, 1 mph (1 km/h) or stopped, and the engine speed is 2,000 rpm or more for about 3 minutes.
- When the engine speed is 500 rpm or less, and the vehicle is traveling at a speed of 6.2 mph (10 km/h) or more for about 3 minutes.
To determine the actual cause of the problem, question the customer about the conditions during which the problem occurred, taking the above conditions into consideration.
Diagnostic Trouble Code (DTC)
- If the CPU cannot be activated, or it fails, the EPS indicator comes on, but the DTC is not memorized.
- The memory can hold a large number of DTCs. However, when the same DTC is detected more than once, the most recent DTC is written over the prior DTC, therefore only one occurrence is memorized.
- The lowest DTC is indicated first. The DTCs are indicated in ascending order, not in the order that they occurred.
- The DTCs are memorized in the EEPROM (non-volatile memory), therefore the memorized DTCs cannot be erased by disconnecting the battery. Do the specified procedures to clear the DTCs.
Self-diagnosis
Self-diagnosis can be classified into two categories:
- Initial diagnosis: Done right after the engine starts and until the EPS indicator goes off.
- Regular diagnosis: Done right after the initial diagnosis until the ignition switch is turned to LOCK (0).
The EPS control unit does these functions when a problem is detected by self-diagnosis:
1. Turns on the EPS indicator.
2. Memorizes the DTC.
3. Stops power assist and manual steering operation resumes.
NOTE:
- When DTC 23 (a problem with the circuit for engine speed signal) is stored, the power assist will return to normal when the control unit detects the engine speed signal and the vehicle speed is 6.2 mph (10 km/h) or above.
- DTCs 21, 22, and 23 the EPS indicator will go off automatically, and the system returns to normal.
Restriction on Power Assist Operation
Repeated extreme steering force, such as turning the steering wheel continuously back-and-forth with the vehicle stopped, causes an increase in electrical current draw by the EPS motor. The increase of electric current causes the EPS motor to heat up. Because this heat adversely affects the system, the control unit monitors the electric current draw of the EPS motor.
When the control unit detects heat build-up in the EPS motor, it reduces the electric current to the EPS motor gradually to protect the system, and it restricts the power assist operation. The EPS indicator does not come on during this function.
When steering torque is not applied to the steering wheel, or when the ignition is turned to LOCK (0) and the EPS motor cools, the control unit will restore the power assist gradually until it's fully restored (after about 8 minutes).
EPS Control Unit Noise
A relay sound or "click" can be heard from the EPS control unit about 30 seconds after the ignition switch is turned to LOCK (0). This sound is normal.
Torque Sensor Neutral Position
The EPS control unit stores the torque sensor neutral position in the EEPROM. The torque sensor neutral position must be memorized whenever the gearbox, the torque sensor, or the EPS control unit is replaced.
NOTE: The torque sensor neutral position is not effected when erasing the DTCs.
How to Troubleshoot DTCs
The troubleshooting procedures assume that the cause of the problem is still present and the EPS indicator is still on. Following the procedure when the EPS indicator does not come on can result in incorrect diagnosis.
The connector illustrations show the female terminal connectors with a single outline and the male terminal connectors with a double outline.
1. Question the customer about the conditions when the problem occurred, and try to reproduce the same conditions for troubleshooting. Find out when the EPS indicator came on, such as while turning, after turning, when the vehicle was at a certain speed, on start up, etc.
2. When the EPS indicator does not come on during the test-drive, but troubleshooting is done based on the DTC, check for loose connectors, poor terminal contact, etc., in the affected circuit before you start troubleshooting.
3. After troubleshooting, clear the DTC and test-drive the vehicle. Be sure the EPS indicator does not come on.
How to Retrieve DTCs Using the HDS (Honda Diagnostic System)
1. With the ignition switch in LOCK (0), connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. Turn the ignition switch to ON (II).
3. '06-09 models; make sure the HDS communicates with the vehicle and the EPS control unit. If it doesn't, troubleshoot the DLC circuit. Testing and Inspection
4. Follow the prompts on the HDS to display the DTC(s) on the screen. After determining the DTC, refer to the DTC Troubleshooting. Do all systems DTC check, and troubleshoot any power train DTCs first.
5. Turn the ignition switch to LOCK (0).
How to Retrieve DTCs (Service Check Signal Circuit Method (Flash codes))
1. With the ignition switch in LOCK (0), connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. Turn the ignition switch to ON (II).
3. '06-09 models; make sure the HDS communicates with the vehicle and the EPS control unit. If it doesn't, troubleshoot the DLC circuit. Testing and Inspection
4. Turn the ignition switch to LOCK (0).
5. Short the SCS circuit to body ground using the HDS.
6. Turn the ignition switch to ON (II).
7. The blinking frequency indicates the DTC. DTCs are indicated by a series of long and short blinks. Add the long and short blinks together to determine the DTC. After determining the DTC, refer to the DTC troubleshooting.
The system will not indicate the DTC unless these conditions are met:
- Set the front wheels in the straight ahead driving position.
- The ignition switch is turned to ON (II).
- The engine is stopped.
- The SCS circuit is shorted to body ground before the ignition switch is turned to ON (II).
8. Turn the ignition switch to LOCK (0).
9. Disconnect the HDS from the DLC.
How to Clear DTCs Using the HDS (Honda Diagnostic System)
1. With the ignition switch in LOCK (0), connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. Turn the ignition switch to ON (II).
3. '06-09 models; make sure the HDS communicates with the vehicle and the EPS control unit. If it doesn't, troubleshoot the DLC circuit. Testing and Inspection
4. Clear the DTC(s) by following the screen prompts on the HDS.
NOTE: See the HDS Help menu for specific instructions.
5. Turn the ignition switch to LOCK (0).
How to Clear DTCs Using the Service Check Signal Circuit Method
NOTE: Use this procedure when the HDS software does not match the year/model vehicle you are working on.
1. With the ignition switch in LOCK (0), connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
2. With the vehicle on the ground, set the front wheels in the straight ahead driving position.
3. Short the SCS circuit to body ground using the HDS.
4. Turn the steering wheel 45 degrees to the left from the straight ahead driving position, and hold the steering wheel in that position.
5. Turn the ignition switch to ON (II). The EPS indicator comes on, then it goes off after 4 seconds.
6. Within 4 seconds after the EPS indicator goes off, return the steering wheel to the straight ahead driving position and release the steering wheel.
The EPS indicator comes on again 4 seconds after releasing the steering wheel.
7. Within 4 seconds after the EPS indicator comes on, turn the steering wheel 45 degrees to the left again and hold it in that position.
The EPS indicator goes off after 4 seconds.
8. Within 4 seconds after the EPS indicator goes off, return the steering wheel to the straight ahead driving position again and release the steering wheel. The EPS indicator blinks twice 4 seconds after releasing the steering wheel, indicating that the DTC was erased.
NOTE: If the EPS indicator does not blink twice, an error was made in the procedure and the DTC was not erased. Turn the ignition switch to LOCK (0), and repeat the operation from step 3.
9. Turn the ignition switch to LOCK (0) within 5 seconds after the EPS indicator blinks twice.
NOTE: If the ignition switch is not turned to LOCK (0) within 5 seconds after the EPS indicator blinks, the system will go to the memorizing mode of the torque sensor neutral position. To avoid this, turn the steering wheel 45 degrees to left from the straight ahead driving position and turn the ignition switch to LOCK (0). This will return the system to the alert mode.
10. Disconnect the HDS from the DLC.
11. Recheck for the DTC to be sure it has been erased.
