Mackpro

Testing the relay by it’s self. 80-140 ohms across pins 1 and 2

Pin 85 should have 12 volts when key turned to start position

Very small relay in kick panel fuse box. It must be inserted correctly or no start. The blades must be horizontal. Not vertical.

Your fuse box down by your clutch pedal, does it have a rubber boot that goes around it that sticks out a couple inches along the side? There was a recall on most all CXU, GU and CHU’s. Water was getting in the fuse box and shorting out relays. https://static.nhtsa.gov/odi/rcl/2014/RCRIT-14V078-3643.pdf

Thoses codes are odd and uncommon. I had no notes in my manual on them.

Sometimes the pictures in the VMAC 3 troubleshooting manual are shown from the wrong end of the connector. Sometimes it’s looking at the front of the connector and sometimes from the rear. Best to check the actual wire number on the wire itself . VJ3-08-0.8

The EPA killed the option of some HP upgrades on some pre 2007 trucks. Mostly on the AI engines in certain years. It wasn’t due to they way the truck was spec’ed , just maxed out their NOX and particulate matter (soot) output for the year on all the vocational trucks they built that year. It happened to several friends of mine back then with their CV’s. I looked your truck up and couldn’t find a torque limit switch on your truck . Usually only saw those on 460’s with 18 speeds .

The engine ECM looks at the coolant temp and intake manifold temp and AC high pressure switch and commands the fan to engage. If you unplug the fan harness connector from the fan the fan should speed up/engage. Coolant thermostat and water pump and radiator clogged externally ( behind after cooler) is the more common over heating problems. Is this a farm use truck?

Mid144 PPID-3 FMI-3 is Starter relay output , voltage above normal or shorted high. Possible cause is short in harness or relay

The small chrome auxiliary starter solenoid/relay that’s bolted to starter is where the magic happens. The small red wire pretty much comes from the key switch and starter relay in the fuse box. The black wire goes back to the engine ecm. These two wires are in a loom together and come off the back of the engine harness and over the top of the transmission. Turn key off and let truck power down . The key on and then to start position. You have one 5 second shot to check the voltage on the red wire . Which should be 12volts. After 5 seconds the VECU kills the starter relay voltage. You have to cycle the key back off to re-test.

The ecm swap should have let it start. Check ground stud that welded to frame behind battery box. Also check the fuseable link ground wire that goes from negative battery to that ground stud. Had weird issues with this wire and stud.

Here’s the bulletin on ride height setting. Covers all but the Mack “Y” ride suspension. Read it carefully and match up what suspension that you have. Also does the truck have a sleeper? https://pdf4pro.com/cdn/service-bulletin-mckenzie-tank-lines-7fe6.pdf

Power comes through firewall on the second connector down , pic C. This is the back of the fuse box . Then it comes through a 16 pin connector up by the foot valve/wiper motor.

The engine ecm controls the ground for the small auxiliary starter solenoid that on the starter. The engine ecm has the final say on whether to start or not by completing the ground. Using a test ecm and if you can now see engine hours then most of the time you have a failed engine ecm. The test ecm could be from a automatic trans truck or be programmed totally different than the original so sometimes they won’t start. I have see a few times that the power and ground were weak to the engine ecm. It might show 12 volts and ground but under a load there is not enough voltage or ground to carry the load .

With all MP engines that won’t crank . First check engine hours in the dash cluster . Usually under Trip Info. If no hours are shown and only hash marks, check the bottom connector on the engine Ecm for power and ground.

Use good DEF fluid ( not out a jug ), keep valves , and injectiors and engine brake plungers adjusted, get DPF filter and cat cleaned every 2 years. Keep EGR differential sensor ports clean. Have dealership check truck for software updates in the engine and after treatment ECM,s. Make sure both nox sensors and the newest part numbers and not counterfeit if they have been replaced. No boost pressure leaks anywhere at all . Newest EGR differential pressure sensor and venture pipe installed . Boost /temp sensor clean and not soot caked. I could keep going for ever but in reality, everything has to be perfectly maintained and operating for the system to be trouble free.

Sometimes there is a sleeper fan switch on the dash or overhead console. This is where the driver can turn the sleeper blower motor on or off while driving. If it’s switched off I believe the rear controls won’t work.

There is only a intake temp sensor ( 2 wires) on the VMAC 1 and VMAC 2 engines. A boost sensor would have 3 wires . The TEM sensor timing event sensor in the side of the pump. Make sure it’s gently screwed in till it bottoms out and gently tighten the jam nut. Lots of people either back the sensor out a half turn or crank down on the jam nut with a 2 foot long wrench and stretch the sensor and ruin it. Also the RPM sensor under the starter that goes into the bell housing. If it’s not adjusted correctly it will cause surging and missing at high RPMS . It to can be streched by over tightened jam nut . Mack says back out the rpm sensor one turn but we usually do 3/4 turn . Also a ETECH flywheel will fit on your engine but cause the rpm sensor not to read . Seen that a bunch .

Awesome information!

What Joey said and also here’s the service bulletin on it . https://f01.justanswer.com/HeavyEquipmentTech/08b3b0a9-699e-422a-b834-ba684bc06d37_Mack_fault_9-2.pdf

Thanks for the information.

I believe that year they look for the parking brake signal from the parking brake switch above the throttle pedal. Is the parking brake light on in the dash when your air brake buttons are pulled out?