I identified the no start condition. This info may be useful to any Prevost owner, as well as DDEC III and IV engines (series 60 and 8V92) of late 90s vintage.
The fault that caused the no start condition is in Circuit 439. Relay 23 is switched hot 12vdc with the ignition key, energizing circuit 439. This circuit passes through connections C115 and C162 to pin B3 on the DDEC 3 ECMs 30 pin connector C160. Somewhere between C115 and C160 circuit 439 is broken. Without this circuit energized, the DDEC doesn't know to turn on and the CEL, SEL and Pro Drive don't work.
I bypassed 439 by running a wire between Relay 23 and pin B3 on C160 and Boom! She started! But..... it turns out circuit 439 ALSO powers the Pro Drive, the DDR connector, and BOTH the CEL and SEL (Check Engine Light and Stop Engine Light). Without power to 439, you cannot read the codes.
So, things to check if your bus of above make and vintage stops running, or will not start AND has no CEL or SEL; First test Relay 23 in the rear junction box. Swap with R13 (foglights) and try to restart. if not, test for power at the right side 30 pin connector wire 439, pin position B3. If the engine cranks but wont start, and the CEL and SEL don't work, it's R23 or a broken conductor on circuit 439.
And the Question: Does anyone know where C162 is located? It's a 4 pin connector with location "Engine DDEC III Accessories". I suspect that's where the corrosion or break is.
Sorry for the rambling ramp up to my question.
Mark
I don't have a Prevost, but they are wired about the same. I fought this problem for almost a year and found that the switch in the rear that is used to turn the engine off when you are working on it or want to stop from the rear had gone bad. It more than likely was because it hadn't been used an had corroded. Flipped the switch a few time and all was fine. I did replace the switch when we got home.
Jack
will look at shop later. I got complete wiring diagram fro prevostcar.com Coach specific. Example last letter in your serial # =year plus last 4 digits= unit number. My 98=W unit = last digits.
Yes, the rear start switch will shut the engine down if its bad!
Bob, I have the wiring diagram from Prevost. I was hoping you might recall the location. I'm looking in the engine bay but you never really know where these connections actually are!
Thanks!
Those firggin DDEC's are broke down into 2 sections the DDEC responsibility and OEM responsibility they can drive you nuts on the OEM side
Go to page P.C 2/2 center slightly right. Comes from foot pedal connector in front then to front junction box and to ddec in rear. Could be the sensor on your foot pedal. Connector c 160 should have paper tag on it. also ck C 115 in rear junction box Deutch connector. Wire from foot pedal goes thru floor to C 160 in front compartment might reach thru steering compartment. C160 is front service compartment interface.
look for wire 161-18 ga
ck circuit breakers 19 20 21 in rear junction box for power. 21 is power for ignition (12V)
Cliff, I agree. The Detroit side of the DDEC 3 is simple. I fixed 8 broken wires to get it running and then purchased a new sensor harness pn 23513558-0 of Ebay for $195. Its the Prevost side that has issues.
I isolated the bad section of 439 to between C115 and C162. Im going to remove that section of the harness (if I can) and repair it.
I still havent figured out why the SEL, CEL and Pro Drive wont work. The tach doesnt work and the speedo's odometer is blank too.
The throttle pedal works.
Circuit Breakers CB19, 20, and 21 are powered with ign switch on.
Today I'll get a few hours in on it.
ck ground to dash/gauges no coincidence that multiples are not working There is also a couple breakers tucked up under dash next to your right knee.. don't remember their function but do remember they lost ground to bracket and quit doing their job. They ground thru their base. Ben awhile on that one.. bob
Bob, thanks for helping with suggestions. It's going to take me quite some time to get the wiring straightened out on this bus. And the suspension. And the brakes. And the interior...... yikes.
The check engine and stop engine lights should have b+ when the switch is turned on. The ECM puts them to ground.
Jack
Quote from: OneLapper on March 04, 2017, 04:32:12 PM
Bob, thanks for helping with suggestions. It's going to take me quite some time to get the wiring straightened out on this bus. And the suspension. And the brakes. And the interior...... yikes.
Yep once they reach that point it takes time and money to resurrect a Prevost from the dead.Mark I have some hard copies of the manuals if you need one PM me and I'll send you one,the manuals do help but Prevost may have 6 different wiring schematics for the same model year
Quote from: blue_goose on March 05, 2017, 04:47:00 AM
The check engine and stop engine lights should have b+ when the switch is turned on. The ECM puts them to ground.
Jack
Yes, you're correct. The fan clutch is the same set up, too.
Quote from: luvrbus on March 05, 2017, 06:47:39 AM
Yep once they reach that point it takes time and money to resurrect a Prevost from the dead.Mark I have some hard copies of the manuals if you need one PM me and I'll send you one,the manuals do help but Prevost may have 6 different wiring schematics for the same model year
Yup, well, dead was what I could afford. The bones are good, as they say! This bus came with tons of spares...... 48 shocks, a dozen air bags, four disc rotors, two drums, pads, shoe linings, dozens of bearings and seals, sensors, spare exterior panels, 36 curtains of all colors, wiper motors, windshields, 16 Norgren valves..... there are boxes I haven't opened yet. Literally pallets of spares. So far I haven't needed to buy a single part from Prevost.
Any manuals you're willing to send my way would be greatly appreciated!
What year is this Prevost you have with all these parts ?
It's a 97 XL 45E
Is the last letter in your serial number a V ?