Honda Civic. Manual — part 504

Fig. 1: Locating EPS Components

GENERAL TROUBLESHOOTING INFORMATION

EPS INDICATOR

Under normal conditions, the EPS indicator comes on when the ignition switch is
turned to the ON (II) position, then goes off after the engine is started. This
indicates that the LED 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.

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 51-01, 51-02 or 51-06 is stored in the control unit, the EPS indicator
will stay on until the DTC is erased. When a problem is detected and the EPS
indicator comes on, there are cases when the indicator stays on until the ignition
switch is turned OFF, and cases when the indicator goes off automatically when the
system returns to normal. Even though the system is operating normally, the EPS
indicator will come on under the following conditions:

The vehicle speed decreases abruptly from 12mph (20 km/h) or more (by
applying brake), and it is less than 1 mph (1 km/h) and engine speed is 2,000
rpm or above for 5 seconds (continuously) after the abrupt deceleration.

While turning the steering wheel with the vehicle speed of 1 mph (1 km/h) or
less for 20 seconds, and the engine speed is 2,000 rpm or above for at least 10
seconds.

When the engine speed is 500 rpm or less, and the vehicle is travelling at a
speed of 6 mph (10 km/h) or more for about 3 seconds.

To determine the actual cause of the problem, question the customer about the
conditions during which the problem occured, taking the above conditions into
consideration.

DIAGNOSTIC TROUBLE CODE (DTC)

2008 Honda Civic EX

2006-08 STEERING EPS System - Civic (All Except Hybrid & Si)

If the CPU cannot be activated, or it fails, the EPS indicator comes on, but the
DTC is not memorized.

The memory can hold any 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 occurance 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 (nonvolatile memory) therefore the
memorized DTCs cannot be erased by disconnecting the battery. Perform the
specified procedures to clear DTCs.

SELF-DIAGNOSIS

Self-diagnosis can be classified into three 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 OFF.

Steering diagnosis: Done during regular diagnosis while turning steering
wheel.

The EPS control unit performs the following 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.

RESTRICTION ON POWER ASSIST OPERATION

Repeated extreme steering force, such as turning the steering wheel continuously

NOTE:

For DTCs 11-01, 11-02, 12-01,21-01,21-02, 22-01 and 35-
04 the EPS indicator will go off automatically, and the
system returns to normal.

2008 Honda Civic EX

2006-08 STEERING EPS System - Civic (All Except Hybrid & Si)

back-and-forth with the vehicle stopped, causes an increase of power consumption
in the EPS motor. The increase of electric current causes the motor to heat up.
Because this heat adversely affects the system, the control unit monitors the electric
current of the motor.

When the control unit detects heat build-up in the motor, it reduces the electric
current to the 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 off and the motor cools, the control unit will restore the power assist
gradually until it's fully restored (after about 8 minutes).

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 motor,
or the EPS control unit is replaced.

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.

1. Question the customer about the conditions when the problem occured, and try

to reproduce the same conditions for troubleshooting. Find out when the EPS
indicator came on, such as during EPS control, after EPS control, when the
vehicle was at a certain speed, 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.

NOTE:

The torque sensor neutral position is not effected when
erasing the DTCs.

2008 Honda Civic EX

2006-08 STEERING EPS System - Civic (All Except Hybrid & Si)

HOW TO RETRIEVE DTCS

1. With the ignition switch to LOCK (0), connect the HDS (Honda diagnostic

system) to the data link connector (DLC) (A) located under the driver's side of
the dashboard.

Fig. 2: Identifying DLC Connector

2. Turn the ignition switch ON (II).
3. Make sure the HDS communicates with the vehicle and the EPS control unit. If

it doesn't, troubleshoot the DLC circuit (see DLC CIRCUIT
TROUBLESHOOTING ).

4. Follow the prompts on the HDS to display the DTC(s) on the screen. After

determining the DTC, refer to the DTC TROUBLESHOOTING.

5. Turn the ignition switch to LOCK (0).

HOW TO CLEAR DTCS

1. With the ignition switch in LOCK (0) position, connect the HDS to the data

link connector (DLC) (A) located under the driver's side of the dashboard.

NOTE:

See the HDS Help menu for specific instructions.

2008 Honda Civic EX

2006-08 STEERING EPS System - Civic (All Except Hybrid & Si)