DTC B1681[IMMOBILIZER SYSTEM (PATS) (AJ (3.0L Duratec))]

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Detection Condition

• No detected communication with the coil antenna.

Possible Cause

• Coil malfunction

• PCM malfunction

• Malfunction in the related wiring harness

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Diagnostic Procedure

STEP

INSPECTION

ACTION

1

INSPECT COIL ANTENNA POWER SUPPLY

•  Disconnect the coil antenna connector.

•  Turn the ignition switch to the ON position.

•  Measure the voltage at coil antenna connector terminal A.

―  Is the voltage 8 V or more?

Yes

Go to the next step.

No

Repair the wiring harness.

2

INSPECT WIRING HARNESS BETWEEN COIL ANTENNA AND GROUND

•  Turn the ignition switch to the LOCK position.

•  Inspect the wiring harness between coil antenna connector terminal B and ground for the following items:

―  Short to power supply

―  Open circuit

•  Is the wiring harness normal?

Yes

Go to the next step.

No

Repair the wiring harness.

3

INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT

•  Connect the coil antenna connector.

•  Turn the ignition switch to the ON position.

•  Measure the voltage at coil antenna connector terminal C.

―  Is the voltage 8 V or more?

Yes

Go to Step 7.

No

Go to the next step.

4

INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT

•  Turn the ignition switch to the LOCK position.

•  Disconnect the PCM connector.

•  Turn the ignition switch to the ON position.

•  Measure the voltage at PCM connector terminal 18.

―  Is the voltage 8 V or more?

Yes

Replace the PCM and perform the resetting procedure for the immobilizer system when replacing the PCM.

(See IMMOBILIZER SYSTEM (PATS) COMPONENT REPLACEMENT/KEY ADDITION AND CLEARING[AJ (3.0L Duratec)].)

No

Go to the next step.

5

INSPECT COMMUNICATION CIRCUIT (INPUT) FOR CONTINUITY

•  Turn the ignition switch to the LOCK position.

•  Disconnect the coil antenna connector and PCM connector.

•  Is there continuity between coil antenna connector terminal C and PCM connector terminal 18?

Yes

Go to the next step.

No

Repair the wiring harness.

6

INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT

•  Measure the resistance between coil antenna connector terminal C and ground.

―  Is the resistance 10 kilohms or more?

Yes

Replace the coil antenna.

(See COIL ANTENNA REMOVAL/INSTALLATION.)

No

Repair the wiring harness.

7

INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT

•  Connect the coil antenna connector and PCM connector.

•  Turn the ignition switch to the ON position.

•  Measure the voltage at coil antenna connector terminal D.

―  Is the voltage 8 V or more?

Yes

Replace the coil antenna.

(See COIL ANTENNA REMOVAL/INSTALLATION.)

No

Go to the next step.

8

INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT

•  Turn the ignition switch to the LOCK position.

•  Disconnect the coil antenna connector.

•  Turn the ignition switch to the ON position.

•  Measure the voltage at coil antenna connector terminal D.

―  Is the voltage 8 V or more?

Yes

Replace the coil antenna.

(See COIL ANTENNA REMOVAL/INSTALLATION.)

No

Go to the next step.

9

INSPECT COMMUNICATION CIRCUIT (OUTPUT) FOR CONTINUITY

•  Turn the ignition switch to the LOCK position.

•  Disconnect the PCM connector.

•  Is there continuity between coil antenna connector terminal D and PCM connector terminal 17?

Yes

Go to the next step.

No

Repair the wiring harness.

10

INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT

•  Measure the resistance between PCM connector terminal 17 and ground.

―  Is the resistance 10 kilohms or more?

Yes

Replace the PCM and perform the resetting procedure for the immobilizer system when replacing the PCM.

(See IMMOBILIZER SYSTEM (PATS) COMPONENT REPLACEMENT/KEY ADDITION AND CLEARING[AJ (3.0L Duratec)].)

No

Repair the wiring harness.

STEP	INSPECTION		ACTION
1	INSPECT COIL ANTENNA POWER SUPPLY • Disconnect the coil antenna connector. • Turn the ignition switch to the ON position. • Measure the voltage at coil antenna connector terminal A. ― Is the voltage 8 V or more?	Yes	Go to the next step.
1		No	Repair the wiring harness.
2	INSPECT WIRING HARNESS BETWEEN COIL ANTENNA AND GROUND • Turn the ignition switch to the LOCK position. • Inspect the wiring harness between coil antenna connector terminal B and ground for the following items: ― Short to power supply ― Open circuit • Is the wiring harness normal?	Yes	Go to the next step.
2		No	Repair the wiring harness.
3	INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT • Connect the coil antenna connector. • Turn the ignition switch to the ON position. • Measure the voltage at coil antenna connector terminal C. ― Is the voltage 8 V or more?	Yes	Go to Step 7.
3		No	Go to the next step.
4	INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT • Turn the ignition switch to the LOCK position. • Disconnect the PCM connector. • Turn the ignition switch to the ON position. • Measure the voltage at PCM connector terminal 18. ― Is the voltage 8 V or more?	Yes	Replace the PCM and perform the resetting procedure for the immobilizer system when replacing the PCM. (See IMMOBILIZER SYSTEM (PATS) COMPONENT REPLACEMENT/KEY ADDITION AND CLEARING[AJ (3.0L Duratec)].)
4		No	Go to the next step.
5	INSPECT COMMUNICATION CIRCUIT (INPUT) FOR CONTINUITY • Turn the ignition switch to the LOCK position. • Disconnect the coil antenna connector and PCM connector. • Is there continuity between coil antenna connector terminal C and PCM connector terminal 18?	Yes	Go to the next step.
5		No	Repair the wiring harness.
6	INSPECT COIL ANTENNA INPUT SIGNAL CIRCUIT • Measure the resistance between coil antenna connector terminal C and ground. ― Is the resistance 10 kilohms or more?	Yes	Replace the coil antenna. (See COIL ANTENNA REMOVAL/INSTALLATION.)
6		No	Repair the wiring harness.
7	INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT • Connect the coil antenna connector and PCM connector. • Turn the ignition switch to the ON position. • Measure the voltage at coil antenna connector terminal D. ― Is the voltage 8 V or more?	Yes	Replace the coil antenna. (See COIL ANTENNA REMOVAL/INSTALLATION.)
7		No	Go to the next step.
8	INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT • Turn the ignition switch to the LOCK position. • Disconnect the coil antenna connector. • Turn the ignition switch to the ON position. • Measure the voltage at coil antenna connector terminal D. ― Is the voltage 8 V or more?	Yes	Replace the coil antenna. (See COIL ANTENNA REMOVAL/INSTALLATION.)
8		No	Go to the next step.
9	INSPECT COMMUNICATION CIRCUIT (OUTPUT) FOR CONTINUITY • Turn the ignition switch to the LOCK position. • Disconnect the PCM connector. • Is there continuity between coil antenna connector terminal D and PCM connector terminal 17?	Yes	Go to the next step.
9		No	Repair the wiring harness.
10	INSPECT COIL ANTENNA OUTPUT SIGNAL CIRCUIT • Measure the resistance between PCM connector terminal 17 and ground. ― Is the resistance 10 kilohms or more?	Yes	Replace the PCM and perform the resetting procedure for the immobilizer system when replacing the PCM. (See IMMOBILIZER SYSTEM (PATS) COMPONENT REPLACEMENT/KEY ADDITION AND CLEARING[AJ (3.0L Duratec)].)
10		No	Repair the wiring harness.