System Operation Description:
Use this procedure under the following situation:
Use this procedure if the electronic service tool will not power up or the electronic service tool will
not communicate with the Engine Control Module (ECM) through the data link connector.
The following background information is related to this procedure:
The ATA data link (American Trucking Association) is the standard data link that is used by the ECM to communicate with electronic service tools. The SAE specification J1587 defines the format of the messages and data that is being communicated. The SAE specification J1708 defines the hardware requirements and the protocol of the serial communications. Some electronic dashboards use this data link to receive information. Some automatic transmissions also receive information from this data link.
The ECM provides the following two ATA data link connection terminals from the ECM vehicle harness connector J1:
• J1:9 (J1587 Data Link Negative)
• J1:8 (J1587 Data Link Positive)
The vehicle OEM provides twisted pair wiring from the ECM to the data link connector.
Remember that there are potentially several devices 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 devices may cause problems with the data link. These problems can disrupt communications to the engine ECM and from the engine ECM.
Communication
When the key switch is in the OFF position, the ECM may communicate with the electronic service tool. The communications may be disrupted and the communications may require frequent reconnection. In order to avoid this problem, turn the key switch to the ON position when the electronic service tool is being used.
The electronic service tool may indicate the following error message:
• The version of the ECM is not recognized and the integrity of the changed parameters and displayed data is not guaranteed.
This message will indicate that the latest version of the electronic service tool has not been installed or this message will indicate that the software in the ECM is newer than the software for the electronic service tool.
A. Thoroughly inspect the following electrical connectors:
• ECM vehicle harness connector J1/P1
• Data link connector
• Firewall bulkhead connector
• Electronic service tool connectors
• ATA data link (terminal 8 and terminal 9) in the connectors
Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.
B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the ATA data link.
C. Check the ECM connector (Allen Head Screw) for the proper torque of 6.0 N·m (55 lb in).
D. Check the harness and wiring for abrasion and pinch points from the connector to the ECM.
Refer to Illustration 44.
Expected Result:
All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or pinch points.
Results:
• OK – Proceed to Test Step 2.
• Not OK
Repair: Perform the following repair:
Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.
Verify that the repair eliminates the problem.
STOP.
Test Step 2. Determine the Type of Problem with the Data Link
A. Connect the electronic service tool to the data link connector.
B. Start the engine.
Expected Result:
Result 1 The engine starts. The electronic service tool powers up and the electronic service tool communicates without error.
Result 2 The engine starts. The electronic service tool powers up but an error is displayed.
Result 3 The engine cranks but the engine will not start regardless of the condition of the electronic service tool.
Result 4 The engine will not crank regardless of the condition of the electronic service tool.
Result 5 The engine starts but the electronic service tool does not power up.
Note: Check the display screen or check the communication adapter display in order to determine if the electronic service tool has powered up. The electronic service tool will display information that shows if the tool is getting power.
If the electronic service tool or the communication adapter powers up, the data link connector is receiving power.
Results:
• Result 1 – There is not a problem with the
ATA data link at this time. If an intermittent condition exists, thoroughly inspect all wiring and connectors.
Repair: Perform the following diagnostic
procedure:
Troubleshooting, “Electrical Connectors – Inspect”
STOP.
• Result 2 – The electronic service tool displays an error message. The ECM is receiving battery power. Proceed to Test Step 5.
• Result 3 –
Repair: Perform the following diagnostic procedure:
Troubleshooting, “Engine Cranks But Will Not Start”
STOP.
• Result 4 –
Repair: Perform the following diagnostic
procedure:
Troubleshooting, “Engine Will Not Crank”
STOP.
• Result 5 – The electronic service tool does not power up or the communications adapter does not power up. Ensure that the ECM is receiving the correct battery power. Proceed to Test Step 3.
Test Step 3. Check the Battery Voltage Supply to the Data Link Connector
A. Turn the key switch to the ON position.
B. Use a multimeter in order to measure the voltage from the + Battery terminal of the data link connector to the ? Battery terminal of the data link connector.
Refer to Illustration 45.
Expected Result:
The voltage is between 11.0 and 13.5 VDC for a 12 Volt system or between 22.0 and 27.0 VDC for a 24 Volt system.
Results:
• OK – The data link connector is currently receiving the correct voltage. Proceed to Test Step 4.
• Not OK – The data link connector is not receiving the correct voltage.
Repair: Inspect the wiring and fuses to the connector. Repair the wiring or batteries and/or replace the wiring or batteries, as required. Send the vehicle to the OEM dealer for repair, if necessary.
Verify that the repair eliminates the problem.
STOP.
Test Step 4. Change Electronic Service Tool Components
A. If another vehicle or another ECM is available with a Caterpillar electronic engine, connect the
electronic service tool to the other vehicle by using the same cables.
B. Turn the key switch to the ON position. Determine if the electronic service tool operates correctly on the other vehicle.
C. If another engine is not available in the shop, find a different set of electronic service tool cables.
Ensure that the set of electronic service tool cables is a complete set.
D. Connect the electronic service tool to the data link connector by using the new cables.
E. Turn the key switch to the ON position.
F. If changing cables allows the electronic service tool to operate properly, use the following procedure:
a. Replace the pieces from the old set of cables into the new set of cables that operates.
Replace one piece at a time.
b. Repower the electronic service tool after each of the pieces is replaced. Use this method to find the faulty piece.
G. If changing cables does not allow the electronic service tool to operate properly, connect another electronic service tool.
H. Turn the key switch to the ON position.
Expected Result:
Result 1 The original electronic service tool works on another vehicle.
Result 2 A different electronic service tool works on the original vehicle while the engine is being tested.
Results:
• Result 1 – Proceed to Test Step 5.
• Result 2
Repair: Send the faulty electronic service tool for repairs.
STOP.
Test Step 5. Check the Battery Voltage at the ECM
A. Ensure that the electronic service tool is connected to the data link connector.
B. Disconnect vehicle harness connector P1 from ECM connector J1 and insert a 140-2266 Cable (Seventy-Pin Breakout).
C. Turn the key switch to the ON position.
D. Measure the voltage between P1:52 (Unswitched +Battery) and P1:65 (?Battery).
E. Measure the voltage between P1:70 (Ignition Key Switch) and P1:65 (?Battery).
Refer to Illustration 46.
Expected Result:
The voltage is between 11.0 and 13.5 VDC for a 12 Volt system or between 22.0 and 27.0 VDC for a 24 Volt system.
Results:
• OK – The ECM is currently receiving the correct voltage. Proceed to Test Step 6.
• Not OK – The ECM is not receiving the correct voltage. Ensure that there is not an aftermarket
engine protection switch that is overriding battery power to the ECM.
Repair: Perform the following diagnostic
procedure:
Troubleshooting, “Ignition Key Switch Circuit and Battery Supply Circuit – Test”
STOP.
Test Step 6. Install a Bypass Harness
A. Turn the key switch to the ON position.
B. Disconnect vehicle harness connector J1/P1 from the ECM.
C. Install an electronic service tool power bypass cable. Connect a bypass harness to ECM
connector J1.
Refer to Illustration 47 for the bypass harness.
Note: This bypass directly connects the circuit for the key switch to the ECM. The ECM will remain
powered until the connection to the unswitched battery line “+” is disconnected. Remove the 20
Amp fuse from the in-line fuse holder to power down the ECM. Do not connect the bypass to the battery posts without first removing the 20 Amp in-line fuse or do not remove the bypass from the battery posts without first removing the 20 Amp in-line fuse.
Expected Result:
The electronic service tool is operating correctly.
Results:
• OK
Repair: Perform the following repair:
There is a problem in the vehicle wiring, or another device in the vehicle is causing problems on the data link. Either determine the device that is causing the problem or send the vehicle to the OEM dealer for repair.
Verify that the repair eliminates the problem.
STOP.
• Not OK – Verify that the 20 Amp fuse in the bypass harness is not open. A fuse that is open is a blown fuse. Proceed to Test Step 7.
A. Connect the battery wires from the bypass harness to a different battery that is not on the vehicle.
Expected Result:
The electronic service tool is operating correctly.
Results:
• OK – The vehicle battery is causing the problem.
Repair: Perform the following diagnostic procedure:
Troubleshooting, “Ignition Key Switch Circuit and Battery Supply Circuit – Test”
STOP.
• Not OK
Repair: Perform the following repair:
1. Temporarily connect a test ECM.
2. Remove all jumpers and replace all connectors.
3. Recheck the system for active diagnostic codes.
4. Repeat the Test Step.
5. If the problem is resolved with the test ECM, reconnect the suspect ECM.
6. If the problem returns with the suspect ECM, replace the ECM.
7. Verify that the repair eliminates the problem.
STOP.