Check Engine - Stop Engine Lights

[gmcbuffalo]

Is there a coin battery in these units somewhere?
Greg

[gmcbuffalo]

I got CEL check engine light

but SEL ?????? engine light?????
Greg

[Richard Barnes]

Stop Engine Light
RB

[phorner]

My bus has a couple of yellow wires that are connected directly to the chassis batteries (not through the disconnects) and it is my understanding that they supply uninterrupted power to the DDEC and possibly the transmission ECM.

IF this is their purpose, and IF you have the same wires, and IF yours are as corroded as mine were, then MAYBE this could be the cause of less than ideal voltage causing your error code.

Just a thought....

[Jon Wehrenberg]

I know this has been discussed previously, but on Richard's vintage coach he is likely to have wires directly connected to the batteries dedicated to the DDEC. Also CB 19, 20 and 21 in the rear electrical box are for the DDEC.

FWIW the wire at the LH rear (going by memory so double check) has a ring terminal and if the batteries and those terminals are not maintained that wire terminal is subject to corrosion, so the batteries can be fully charged, but the corrosion and resistance from that can drop the voltage to the DDEC.

The first thing that came to mind when I saw the 46 code was to check the equalizer. If it has failed it is possible the 12 volt side of the chassis batteries may be low on voltage. Also check to make sure one of the above CBs has not tripped. Usually if they trip the bus just stops. No warning.

[Richard Barnes]

Jon,

I had new chassis batteries installed by Interstate last month and when I checked them this morning one of the batteries checked in with 7.2 volts and the remaining ones were all at 12.6 to 13.2. I hope a bad battery is all that it is. It appears that Steve and you were correct about a direct 12v connection from one battery to the ECM. I checked the connection for corrosion and there was none. The connection to the ECM was also clean and free of dirt. The 12v direct connection to the ECM was also the battery that showed the low voltage. Interstate's service centers are all closed this weekend but I'll change the battery out early next week and see if that corrects the problem. Thanks again for your help.

[stevet903]

Check your equalizer - it is supposed to keep the charge on the batteries equal. There are troubleshooting instructions in the manuals located here:

http://www.vanner.com/vp/manuals.htm

If the batteries are new, maybe the equalizer didn't get hooked up properly when the battery was replaced?

Steve

[stevet903]

Here's a link to the troubleshooting procedure for code 46.

http://www.tpub.com/content/trucktra...302-20_561.htm

It involves checking the voltage at the ECM with a voltmeter. The ECM runs on 12V, not 24V, so there is a tap between the chassis batteries to provide the 12V. Not sure on yours, but mine has a Vanner equalizer to keep both sets of batteries equally charged. Possible issues are a dirty/corroded ECM plug, bad or undercharged chassis battery, dirty/corroded battery cables or ECM connection to the battery or a defective Vanner (or whatever equalizer you have). Good luck !! Steve

[stevet903]

Stop engine light.

As for a coin battery, I know that the DDEC II does not have one (I've had the ECM open!!). I believe that later ones do not have one either - they are (supposed to be) continually connected to the battery. Later DDEC versions have a data storage capability, and they write the data at the when the engine is turned off. There was a service bulletin that dealt with data loss when the ECM was incorrectly wired and the ignition cut the battery supply to the ECM as the engine was turned off.... I make the assumption that this means that they have no battery backup inside the ECM.

[gmcbuffalo]

Thanks Steve