1996/04/19 Caterpillar

Things To Check BEFORE Replacing An Electronic Control Module (ECM){1901}

Usage:

3406E (5EK),
3176B (9CK),
C-10 (2PN),
C-12 (1YN) Truck Engines

Occasionally, good ECMs are replaced despite the best efforts of the technician. Some of the more common reasons why good ECMs are replaced are listed below along with suggestions on how to make sure the problem is fixed right the first time. ALWAYSuse Electronic Troubleshooting, 3176B, C-10, C-12, and 3406E Truck Engine, SENR5582, as a guide when troubleshooting.

Can't communicate with the ECM.

*Has the ECM been FLASHED? A new ECM contains a blank personality module and will not communicate until FLASHED.

*Have you checked the ± battery connections to make sure the ECM is getting power?

*Are your communications cables and service tools in good working order? Will the same service tool and cables communicate with an ECM on a different truck?

*Use a test ECM and harness to bypass the OEM ± battery and data link wiring.

The Fan is always ON or always OFF.

*Are you sure the OEM chassis uses the engine ECM to control the fan?

*Use the "Cooling Fan Driver" special test on an electronic service tool.

*Are you sure that the ECM is what is keeping the fan ON or OFF? Frequently an OEM device or wiring is the cause of the fan always staying ON or OFF. A new ECM may appear to fix the problem, but the problem may return when the engine warms back up or cools off.

*There are numerous conditions that are supposed to keep the fan ON or OFF. For a list of these conditions, refer to the System Operation section at the beginning of the Cooling Fan Circuit Test in the Electronic Troubleshooting Guide.

The ECM won't turn the fan on when needed by the air conditioning high pressure switch.

*Most trucks are not wired so that the ECM monitors this switch. Refer to the OEM wiring diagram to see how the switch is wired.

*Some trucks are wired so that the engine ECM monitors the status of the air conditioning high pressure switch. On these trucks ONLY, software prior to JUN95 may not turn the fan on when required by the air conditioning system. Fix by FLASHING in JUN95 or newer software.

The problem may be in the software/personality module.

*When you tried the new ECM and the problem went away, did you accidentally fix the problem by FLASHING new software into it? Try FLASHING new software into the "old" ECM.

Vehicle Speed Faults 84-08 and 84-10

*The 3E-0360 and 108-0491 ECMs are susceptible to electrical interference in the vehicle speed circuit. When interference is present the ECM may log vehicle speed faults, kick out of cruise, limit RPM, etc. This problem was fixed with the 117-8351 and newer ECMs, but there are many older ECMs currently in service. Older ECMs with vehicle speed faults should have a 117-7213 Control Group (Vehicle Speed Filter) installed before any other troubleshooting is attempted (see Truck Engine News, September 1994, Page 6, "117-7213 Control Group (Vehicle Speed Filter) Available For Field Installation".

Jake Brake faults 121-05 and 122-05 on engines that do not have Jake Brakes

*FLASH in NOV95 or newer software and program the Engine Retarder Minimum Vehicle Speed to 127 MPH. This solution works ONLY on trucks NOT equipped with a Jake Brake.

Logged injector faults when there are NO performance problems like Missing, etc.

*FLASH in NOV95 or newer software. This software has an improved fault logging strategy and will eliminate complaints where there are no problems except for the diagnostic lamp coming on. If there ARE performance problems or if the fault is active follow the standard procedure in Electronic Troubleshooting, 3176B, C-10, C-12, and 3406E Truck Engine, SENR5582.

If the problem is eliminated by installing a new ECM or Test ECM on the engine, ALWAYS verify that the problem returns when the original ECM with NEW software is reinstalled.

Read Truck Engine News, Technical Information Bulletins, and Tech Tips.

*Your problem probably is not unique. Most unusual problems that are not identified in the Electronic Troubleshooting guide have been discovered and fast, inexpensive solutions are published in these timely documents.

*If you think you do have a new problem or you can not remember where you read the solution to your problem, please call your telephone analyst. They are here to help you!