Community Forums

mel s · 08-12-2011, 06:17 PM

My Cat dealer changed the ECM exhaust brake parameters from "Manual" mode to "Latch" mode.
For some reason the PacBrake operation did NOT change.

In an attempt to get "Latch" to operate, he then "flashed" the ECM, changing the software from the original, (JUL95), to the most current for my engine, (JAN00).
Again no change, still in "Manual"

A few days later he changed the "Latch" mode to "Coast".
The PacBrake is STILL operating in the "Manual" mode.

The dealer is stumped, does not have a next step!

Does anyone have any suggestions or ideas, other than purchasing and installing the BrakeSwitch that is commercially available? ($90 on-line).

I have driven this coach, using the PacBrake set to "Manual", mode for 122,000 miles, I can live without the change, if I have to!

Mel
'96 Safari, 250hp Cat, 3126

HarleyWJones · 08-14-2011, 12:33 AM

I weighed in on this one once before, but I am happier than ever with my change to the ad-on switch.

Here's a link to my previous post - its #4: http://www.irv2.com/forums/f124/exha...tml#post807029

bsimonds · 08-19-2011, 07:34 PM

I have the same problem as the OP. I asked the CAT service folks to program the ECM for "latch mode". They said it was already in Latch mode but it still operates as manual mode.

aztortuga · 08-20-2011, 09:32 AM

In order for the exhaust brake to work while in latch mode, the cruise control must be turned to the on position. I just mention this in case. If the cruise control is in the off position the exhaust brake operates as if it was in the manual mode.

bsimonds · 08-20-2011, 11:45 AM

Tried both Cruise ON and OFF and exhaust brake acts the same.

mel s · 08-26-2011, 09:22 AM

UPDATE:
I installed a BrakeSwitch and it is great! Brakeswitch, A better way to manage your diesel exhaust brake
I recommend a preliminary phone call to Homer Hawks (who IS Brake-Switch) to discuss your particular application.
Homer Hawks
PO Box 3713
Mooresville, NC 28117
Phone - 888-349-5414
Fax - 704-696-0125
Email - hhawks@msn.com
Mine required a blocking diode, I ordered 5 for $2 +$3.50 shipg, from West Florida Components: Your Source for Electronic Parts and Supplies
Both orders took 3 days to WI via USPS.
Mel

Kbiddick · 04-02-2012, 03:30 PM

On my rig there is a bosch relay that disables the Cruise Control (CC) whenever the brake is applied or the Exhaust brake is engaged. When the engine was set to latched mode it acted like it had originally -- whenever the Exhaust brake was enabled it forced a downshift and closed the exhaust valve.
I think it was wired this way because the manufacturer did not include a service brake Sensor signal to the ECM.

In order to not have the CC disabled when I turned on the Exhaust brake I had to re-wire the Cruise control disable relay. Now it only disables the CC when I apply the brakes.

Since the ECM does not know when the service brake is applied, the resume of CC does not function once the brakes are applied and then the accelerator is applied as the Latch mode is described. I have to hit the resume button on the CC.

1ciderdog · 04-02-2012, 05:19 PM

I installed the switch mentioned in post 6 above. It works very well and I am pleased. I had asked both Allison & CAT about programming the original installation for the latch (or a different mode) and neither wanted to do it. Said if I could live with it the way it was that it was best not to flash or change it. I suspected they had had difficulties with the procedure and didn't want to take a chance.