I have a 2005 monaco with a allison 2500MH driven by a cummins ISB 300. The trans would not go into 5th. gear. The only code it showed on the trans side was a fail code p2773. this means the engine is ignoring the trans request for a torque derate. There was never a fault on the engine side and the only light that came on on the dash was the trans light.
I had it in a cummins shop for 21 days . they could never find the problem and walked away from a $3500.00 bill(new ecm/tech support/allison support /labor etc.)
I took it to a cumminc Dealer and a mechanic had a similar problem a year ago. i t took him two days at $120.
an hour to figure it out.
When I brought my coach in he changed the exhaust pressure sensor and found it full of water,removed sensor tube and blew it out. He replaced the exhaust pressure sensor and data shows 29.4 INHG
Trans works fine
For you tech savy guys the answer is this (if I have it right)
he hooked up insite and monitored data with key on but engine not running. barometric pressure is correct but exhaust pressure reads 23 INHG when it should read 29.4 INHG. The INHG is at the low end of the approved rang so it did not send a code to the ECM. The engine thought the coach was in a high altitude so it did not derate the torque. the mechanics last comment on the invoice was---the exhaust gas pressure sensor reading incorrectly was causing the ECM to make incorrect calculations and ignore the trans request for torque derate so it could shift properly!!!!!!!!!!!!!!!!!!!
i hope you all pass this along. This could save us all a lot of down time and money!!!!!!!!!!
the sensor swith was $112.00 plus 1.5 hours labor!!!!!!!!!!!!!!!
Good luck out there, fixit
I had it in a cummins shop for 21 days . they could never find the problem and walked away from a $3500.00 bill(new ecm/tech support/allison support /labor etc.)
I took it to a cumminc Dealer and a mechanic had a similar problem a year ago. i t took him two days at $120.
an hour to figure it out.
When I brought my coach in he changed the exhaust pressure sensor and found it full of water,removed sensor tube and blew it out. He replaced the exhaust pressure sensor and data shows 29.4 INHG
Trans works fine
For you tech savy guys the answer is this (if I have it right)
he hooked up insite and monitored data with key on but engine not running. barometric pressure is correct but exhaust pressure reads 23 INHG when it should read 29.4 INHG. The INHG is at the low end of the approved rang so it did not send a code to the ECM. The engine thought the coach was in a high altitude so it did not derate the torque. the mechanics last comment on the invoice was---the exhaust gas pressure sensor reading incorrectly was causing the ECM to make incorrect calculations and ignore the trans request for torque derate so it could shift properly!!!!!!!!!!!!!!!!!!!
i hope you all pass this along. This could save us all a lot of down time and money!!!!!!!!!!
the sensor swith was $112.00 plus 1.5 hours labor!!!!!!!!!!!!!!!
Good luck out there, fixit