Community Forums

smd1x1 · 01-20-2018, 10:31 AM

I started the bus up today and a amber check info light came on and the rpm gauge and def gauge are not registering. When the key is on and engine not running the dash reads TCM Comm error. Any ideas I afraid to drive it. I asked this question on the tiffin forum also.

BFlinn181 · 01-20-2018, 10:39 AM

It's a bit hard to help with so little information. What's the make, model of your RV? Chassis? Engine details? Is the amber light an icon or have words on it? Look up the icon and identify it for us.

smd1x1 · 01-20-2018, 11:26 AM

2018 allegro bus 37 Ap 450 Cummings powerglide
I turned off all batteries and inverter to try to reboot no help. Started engine 3 times quick and waited 5 min restarted no work.i still get TCM COMM error ECM COMM error ABS COMM error and check info light on. Also DEF and RPM gauge not registering

cruzbill · 01-20-2018, 11:32 AM

Brand new coach? Call Tiffin!!

smd1x1 · 01-20-2018, 11:37 AM

Yeh tried tiffin closed today

BFlinn181 · 01-20-2018, 01:38 PM

ECM is Engine Control Module TCM is Transmission Control Module ABS is Anti-lock Brake Module. To have all three modules in error, I'd suspect a loose connector. If you go to each module and pull each connector, spray with contact cleaner, then reconnect, I bet the issue goes away or at least one or two will now communicate with the others. Comm errors are often power or bad ground issues, another area to check.

If it is still under warranty, let the proper shop do the work, this could eat up shop time tracking it down.

smd1x1 · 01-20-2018, 02:03 PM

Quote:

Originally Posted by BFlinn181

ECM is Engine Control Module TCM is Transmission Control Module ABS is Anti-lock Brake Module. To have all three modules in error, I'd suspect a loose connector. If you go to each module and pull each connector, spray with contact cleaner, then reconnect, I bet the issue goes away or at least one or two will now communicate with the others. Comm errors are often power or bad ground issues, another area to check.

If it is still under warranty, let the proper shop do the work, this could eat up shop time tracking it down.

where can I find modules

Skip426 · 01-20-2018, 02:27 PM

ECM is on the passenger side of the engine .
TCM location is usually in the rear of the coach and Will have Allison logo , may be similar to the picture below .
Anti lock controller MAY be above the differential ,attached to the frame.
Having a problem with all three , you may have to look for a major wiring connector , between the engine/transmission and the frame wiring harness.

jimnrose · 01-21-2018, 12:59 PM

To have all three units fail at the same time is suspicious. I would check the fuses to see if anything has popped.

**Lt Dan** · 01-21-2018, 02:38 PM

The Power Glide chassis operates on a Multiplex BUSS system with some of the control modules in the right rear compartment and some in the front left compartment. With all failing at once, it sounds like a connector has worked loose on one end of the wiring harness. The first thing to check is see if the red LEDs are flashing on the front and rear modules. If not, I would check the main fuses in the right rear and all of the Spyder breakers in the front left bay. Next, I would check all of the connections to each of the modules and see if any have worked loose. You can kill the battery power to all of the chassis functions with the chassis disconnect in the right rear then maybe unplug and plug back in the connectors to check for a loose contact. If not there, then it could be a loose connection in the harness going to the engine/transmission.

Here is a photo of the main chassis power panel. I think the ABS module is the WABCO module on the right. The VANSCO modules on the left are power output controls (I think).

trx430ex · 01-21-2018, 09:44 PM

X 2 check frame to chassis ground.

smd1x1 · 01-22-2018, 03:50 AM

All great information but this problem is beyond me at this point I will call tiffin when they open today. One question I never asked is the bus drivable like this

Skip426 · 01-22-2018, 12:13 PM

Quote:

Originally Posted by smd1x1

All great information but this problem is beyond me at this point I will call tiffin when they open today. One question I never asked is the bus drivable like this

With questionable communication between the controllers for the engine and transmission and the dash ; personally I wouldn't trust the coach to keep running/moving, to get you to a service center.

smd1x1 · 01-23-2018, 09:36 AM

problem is solved. Nathan in the chassis department said go to set up scroll down to Can Baud if it is set on 250 should be 500 so I set to 500 and all is well. I have no idea how it got set to 250 he said I might have done while scrolling other issues. I also told him while searching for loose connections under the bus I noticed another cracked hose clamp he suggested I bring it in and have all hose connections checked. I will post pics of hose clamps when I figure out how to post pics.