Cummins Engine Repair- ISC Engine Code 434

Cummins Engine Repair not only involves mechanical but electronic repairs as well. The ISC model has an ECM that sends and receives messages that controls every performance aspect of this engine. The main source of power is the battery that depends on wiring that feeds the Cummins ECM sufficient voltage to run the engine systems.
Pictured is the laptop shot of an active code #434 a power interruption that derated the engine to a crawl. Derating protects the engine from sustaining high speeds and rpms which would cause more severe damage. This ISC Cummins Engine is in a 1999 Thomas School Bus Saf-T-Liner. With an active code you can retrieve it with the diagnostics switch [on the dash] & ignition switch turned on. The code will beep each number with a pause, in this case 4 beeps 3 beeps 4 beeps with a pause in between each #.

A closer look [click on photo to enlarge] shows numerous fuses on the positive feed wire to the Engine ECM [electronic control module]. Our code information is telling me there is a power problem so "the first thing to check is the Source."

Using a digital ohmmeter check the fuses for continuity and clean all the connections.

Note: Before this maintenance step I could not get a reading on my laptop, there was a communication error between the engine and the "Cummins Insite" software.
After cleaning all the connections and testing the batteries the communication problem was erased and the code disappeared.

There is a variety of 7.5 and 10 amp fuses inline with battery to ECU supply power. I traced the wiring back along the frame as well to check out any other possible problems. The rule of thumb in this situation is to check connections and wiring closest to the environment and work your way up the line.

Using a Snap-On Micro Vat Battery Tester I concluded that all the batteries were in good condition. This tester does a very quick assessment of battery condition and also tests starting and charging systems quickly.

The Conclusion to this problem was simple, servicing the battery connections which had enough resistance to cause the #434 code to occur. It makes sense since the ECM reads Voltage at a very sensitive level.

After an extensive road test the code did not come back and this experience was a good one telling me [and you the reader] to always check the simple things first!

Now we're ready for the next challenge with Cummins Engine Repair.

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