JoeH

A buddy of mine voted for Biden and stands behind the vote. Thinks Biden is awful, but couldn't stand trump's outcries against election gerrymandering and mean tweets. Personally I think the mean tweets were Trump's flashlight to shine on all the rats swimming in the swamp!

My suspicion is that the wire end and possibly sensor melted a bit, and got deleted.

Wound up being real easy: Double check on my Mack Flash Drive P/N 23-021 (has every wiring harness of every Mack chassis from 2000 to about 2020/2021) to compare the switch circuit/wire codes from the 2000 MR688 donor truck to my 2003 I'm working on. Circuit identical. Found wire VJ1-10-0.8 on the 2000 harness which is on my shelf. Appears to go to parking knob area. Got 2000 MR688 dash panel out of storage box, park knob has 2 sensors on it! Went to my 2003, only has one sensor, but has a plug in other port! Found wires nearby, VJ1-10-0.8 is intact, taped to its pair 17-A-0.8 which has been cut short and the end electrical taped. "Borrowed" a sensor from the 2000 dash park knob which I hate doing, but I used the label maker to leave a note for future use; repaired wire end 17-A-0.8 plugged it all together and ran the test light. System functional, I'll be heading to the dealer hopefully today to get the software side cleaned up! Will post results later!

Once again shame on those around Joe. Came across a news article he may have crapped his pants on stage in front of the French president? Absolute shame on everyone around him parading him around when he's this far gone. I get it most of us don't like the guy in the first place, but we at least should recognize his human dignity and call out the people puppeting him around. Retire him and surround him with his loved ones and call it a day. Give the reins over to VP Llama already.

Best bet is to find a truck online with the setup you want, and borrow the VIN to order the part from a Mack dealer in Venezuela.

Then it's back to the dealer for them to try again.

Even if this were a manual trans with a clutch I couldn't switch set the idle without VJ1-10-0.8 receiving parking brake signal. It can enter the reprogram mode without the park brake signal, but can't program a new idle without it. Worst case scenario I just have to plumb in a new park brake switch receiving power from 10amp circuit breaker #17 to one side of a park brake switch, and wire VJ1-10-0.8 on the other side of the switch.

They can't change anything til the VECU registers that the parking brake is set. I need to trace wire VJ1-10-0.8 to find the missing parking brake sensor. I found the wire by the VECU, just need to cut a boatload of zip ties so I can follow it.

Is this even a Mack engine? A little more info on year/engine would be helpful

From the vmaciii 8-211 manual. Schematic for MR parking brake blink code 7-2. I don't have the blink code, that's only tripped when park brake is set while moving.

One problem I've heard with V8's in general is that you have 2 connecting rods on each journal of the crank. But I think the E9's weak spot is the heads.

Worth noting, while the park brake dash lamp works, it does not operate the brake lights.

17-A-0.8 is split down from 17-A-1.0, which comes from Fuse 17, 10amp. This fuse supplies several functions.

Also the switch function requires parking brake to be set anyway, so this is a moot point. Gotta fix/hotwire VJ1-10-0.8. any recommendations on lying to that circuit? I'll post a picture of the schematic.

Lol, I thought about that, but the shop foreman didn't think that would work as it's programmed for an automatic. I'm not opposed to trying it but I don't want to fry anything. The task at hand is to find/repair the "VCU Park Brake Switch" circuit. It's wire VJ1-10-0.8. I found the wire near the VECU, but I need to find where the VCU park switch is. So the dash instrument cluster has a parking brake lamp that functions, it works off the park brake sensor on the park brake knob. However, according to my wiring diagrams for the truck there should be a VECU park sensor. Any suggestions on where it'd be on an MR688?

Never ending. Dealer computer can't program idle speed because VECU isn't picking up that the parking brake is set, even though the dash indicator light comes on saying the parking brake is set. 🤣 Brought the truck home to dig into this myself....

What year is the truck? In general these are fantastic engines, if a bit small compared to modern engines. Weak point on these is the valve lifter tappets. They use a carbide face welded on. The carbide can crack, drop a piece off, then shave the lobe off the cam rather quickly. You'll hear a misfire and when you pop the valve covers one rocker will have excess lash from the missing lobe. Someone said on here recently that the E7 motor lifters are interchangeable?? But I am unfamiliar with this detail. Camshaft might be available through PAI. As long as you don't try and squeeze more HP out of the engine it should be very reliable. Mack engineered these engines to the perfect balance of durability and power. Deviating towards power will quickly sacrifice reliability.

The wealth of knowledge here seems to never end. Thank you @fjh! You pointed me in the right direction to sniff this document out!

Throwing this out into the abyss... Idle speed is adjustable by driver, assuming the feature isn't disabled. Punching the right cruise control sequence enters the "reprogram mode", and as you say you need a clutch pedal to set it once you've floated it where you want it. Or you need the Handy Dandy Mack software, which I sort of have but can't utilize because it doesn't recognize the DieselLaptops interface device I own.

Then how did it change in the first place??

Can I reset it with switches myself??

My 2003 MR688S AI350/Allison hd4560 suddenly just dropped it's low idle speed from 650 down to 500 or less. No codes, just had a ton of engine work done at the dealer, see my other "rollover" thread under Modern Trucks. Been running great til now. Firing up computer to check stats, and doing a visual inspection. Any recommendations?

Fan takes power from engine but also pushes you forward.... Like an airplane.Though it's probably inefficient. You should run 180°F thermostat, if the engine runs too cool unburnt fuel can gum up valves, exhaust, etc when idling.

Pistons are usually done in balanced sets. The C probably dictates what weight tolerance range the pistons are in.

Sounds awful trying to pull both heads together. Glad you have the service crane for it though.