ATA (SAE J1587 / J1708) Data Link Circuit

161

TM 9-2320-312-24-2

Troubleshooting Section

Repair: Repair the wiring from the connector P501

i01631745

for the air inlet heater relay to the ECM connector

ATA (SAE J1587 / J1708) Data

P2. Verify that the problem has been resolved.

Link Circuit - Test

STOP.

SMCS Code: 1408-081; 1901-081

No Proceed to Test Step 12.

System Operation Description:

Test Step 12. Test the Battery Voltage to

the ECM

Use this procedure under the following situation:

A. Turn the ignition key switch to the OFF position.

Use this procedure if ET will not power up or ET

will not communicate with the ECM through the cab

B. Disconnect the ECM vehicle harness connector

data link connector.

J1/P1 and install a breakout T.

The following background information is related

C. Connect a voltmeter between terminal 52 of the

to this procedure:

breakout harness and terminal 65 of the breakout

harness. Refer to Illustration 35.

The ATA data link (American Trucking Association)

is the standard data link that is used by the

D. Turn the ignition key switch to the ON position

ECM to communicate with electronic service

and check the voltmeter.

tools. The SAE specification J1587 defines the

format of the messages and data that is being

E. Turn the ignition key switch to the OFF position.

communicated. The SAE specification J1708

defines the hardware requirements and the protocol

F. Connect a voltmeter between terminal 53 of the

of the serial communications. The Caterpillar

breakout harness and terminal 67 of the breakout

Electronic Technician (ET) is an example of one

harness. Refer to Illustration 35.

of the electronic service tools. Some electronic

dashboards use this data link to receive information.

G. Turn the ignition key switch to the ON position

Some automatic transmissions also receive

and check the voltmeter.

information from this data link.

Expected Result:

The ECM provides the following two ATA data link

connection terminals from the ECM vehicle harness

The voltage is between 11.0 VDC and 13.5 VDC

connector J1:

when the ignition key switch is in the ON position.

Terminal 9 (J1587 DATA LINK NEGATIVE)

Results:

Terminal 8 (J1587 DATA LINK POSITIVE)

Yes

The vehicle OEM provides twisted pair wiring from

Repair: Replace the ECM. Verify that the problem

the ECM to the cab data link connector.

is resolved.

Remember that there are potentially several devices

STOP.

that are installed in the vehicle and remember that

these devices are connected to the ATA data link

at one time. These devices include dash displays,

trip recorders and transmission controls. These

Repair: Inspect the vehicle wiring. Repair the

devices may cause problems with the data link.

vehicle wiring or send the vehicle to the OEM

These problems can disrupt communications to the

dealer for repair. Verify that the problem has been

engine ECM and from the engine ECM.

resolved.

Communication

STOP.

When the ignition key switch is in the OFF

position, the ECM may communicate with ET.

The communications may be disrupted and the

communications may require frequent reconnection.

In order to avoid this problem, turn the ignition key

switch to the ON position when ET is being used.

The Caterpillar Electronic Technician (ET) may

indicate the following error message: