Check For Open Circuit

(a) For an open circuit in the wire harness in Fig. 1, check the resistance or voltage, as described below.

D100788E01

(b) Check the resistance.

(1) Disconnect connectors A and C, and measure the resistance between them. Standard resistance (Fig. 2)

(b) Check the resistance.

(1) Disconnect connectors A and C, and measure the resistance between them. Standard resistance (Fig. 2)

Tester Connection

Specified Condition

Connector A terminal 1 - Connector C terminal 1

10 kQ or higher

Connector A terminal 2 - Connector C terminal 2

Measure the resistance while lightly shaking the wire harness vertically and horizontally. If the results match the examples above, an open circuit exists between terminal 1 of connector A and terminal 1 of connector C.

(2) Disconnect connector B and measure the resistance between the connectors. Standard resistance (Fig. 3)

Tester Connection

Specified Condition

Connector A terminal 1 - Connector B1 terminal 1

Below 1 Q

Connector B2 terminal 1 - Connector C terminal 1

10 kQ or higher

If the results match the examples above, an open circuit exists between terminal 1 of connector B2 and terminal 1 of connector C.

(c) Check the voltage.

(1) In a circuit in which voltage is applied to the ECU connector terminal, an open circuit can be checked by conducting a voltage check. With each connector still connected, measure the voltage between the body ground and these terminals (in this order): 1) terminal 1 of connector A, 2) terminal 1 of connector B, and 3) terminal 1 of connector C. Standard voltage (Fig. 4)

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

5 V

Connector B terminal 1 - Body ground

5 V

Connector C terminal 1 - Body ground

Below 1 V

If the results match the examples above, an open circuit exists in the wire harness between terminal 1 of connector B and terminal 1 of connector C.

SHORT

3. CHECK FOR SHORT CIRCUIT

(a) If the wire harness is ground shorted (Fig. 5), locate the section by conducting a resistance check with the body ground (below).

Fig. 7

(b) Check the resistance with the body ground.

(1) Disconnect connectors A and C, and measure the resistance.

Standard resistance (Fig. 6)

(b) Check the resistance with the body ground.

(1) Disconnect connectors A and C, and measure the resistance.

Standard resistance (Fig. 6)

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

Below 1 Q

Connector A terminal 2 - Body ground

Measure the resistance while lightly shaking the wire harness vertically and horizontally. If the results match the examples above, a short circuit exists between terminal 1 of connector A and terminal 1 of connector C.

(2) Disconnect connector B and measure the resistance.

Standard resistance (Fig. 7)

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

10 kQ or higher

Connector B2 terminal 1 - Body ground

Below 1 Q

If the results match the examples above, a short circuit exists between terminal 1 of connector B2 and terminal 1 of connector C.

4. CHECK AND REPLACE ECU

NOTICE:

• The connector should not be disconnected from the ECU. Perform the inspection from the backside of the connector on the wire harness side.

• When no measuring condition is specified, perform the inspection with the engine stopped and the ignition switch ON.

• Check that the connectors are fully seated. Check for loose, corroded or broken wires.

(a) First, check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. Temporarily replace the ECU with a normally functioning one and check if the problem symptoms occur. If the problem symptoms disappear, replace the original ECU.

(1) Measure the resistance between the ECU ground terminal and body ground. Standard resistance: Below 1 Q

Example:

Ground

I00DDD00 I00DDD00

DDDDD DDMO

□□□□□□□ □□□□□□□

Ground

ECU Side

nr—in

P r-n 1

nMn

: i=i c

=i 1-11=

Wire Harness Side

Ground

Ground

Ground

(2) Disconnect the ECU connector. Check the ground terminal on the ECU side and wire harness side for bending, corrosion or foreign matter. Lastly, check the contact pressure of the female terminals.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

Get My Free Ebook


Post a comment