No throttle .Please help.

[R.E.D]

So while I was driving down the road the truck lost throttle.The pedal is completely dead along with the rpm gauge.Fault code is 6-4.I checked the connectors in the abs computer near the injector and the vecu in the cab.both show no corrosion. Also the triangle connector coming out the firewall.truck is idling higher than normal and the key won't shut the engine off until 15 to 20 second after the key is in the off position.Please advice on what further steps can be taken.truck is 98 ch 355hp

[41chevy]

From Mack Information System:

Blink code 6-4: J1939 serial data line

Failure Mode Identifier FMI: 8 (Abnormal)

Parameter Identification: S231

Message Identification MID: 128 (Abnormal), 142 (Abnormal)

Circuit Description: The V-MAC III system uses the J1939 data line to control communication between the Vehicle Electronic Control Unit (VECU), Engine Electronic Control Unit (EECU), Anti-lock Brake System Control Unit, Allison Transmission Control Unit, and accessory systems, depending on vehicle model and option content. The J1939 data line is an expandable data bus, allowing the addition of accessory control modules (Collision Avoidance, Traction Control, etc.) to be connected to the circuit. The J1939 data line is comprised of two circuits; the L circuit and the H circuit. The two wires are twisted together to prevent outside electrical noise from interfering with the data being carried by the L and H circuits. The V-MAC III system is designed to allow continued engine operation with the loss of the J1939 data line signal as long as the J1587 data line is still operational.

Code Setting Conditions: If either the Vehicle Electronic Control Unit (VECU) or the Engine Electronic Control Unit (EECU) loses communication on the J1939 data line for more than one half second, code 6-4 will set and the Electronic Malfunction Lamp (EML) will turn on. The fault will become inactive if communication resumes for at least on half second. When code 6-4 is active, engine speed will default to 900 RPM. If communication is lost on both the J1587 and J1939 data lines the engine will not run.

Fault code 6-4 will set for some mismatches of VECU and EECU software levels. Blink code 6-4 will also set while the VECU is in the programming mode for Customer Data, Fleet Data, or Mack Data. This code setting condition is normal and the code will become inactive after the ignition key is cycled.

Fault code 6-4 may log, without illuminating the Electronic Malfunction Lamp (EML), on vehicles equipped with Eaton/Bosch ABS/ATC module # 7MN54M2. This nuisance code will not affect the performance of the vehicle. When a vehicle equipped with this ABS/ATC module is being diagnosed for an inactive code 6-4, contact Mack Trucks Service Engineering.

Additional Symptoms:If communication is lost on just the J1939 line, the engine will only run at 900 RPM, no throttle response above 900 RPM

[R.E.D]

So which one is the j1939.is it connected to the vecu?or the one next to it?there are two cables that are wrapped individually with some kinda foil on the inside of the plastic lining.they go to a 3 prong connector.are thy it?.is there an easier way to troubleshoot?thanks 

Red

[41chevy]

That is the shielded data link cables ,do not damage the foil as it cuts outside interference with the  data stream. . With out a scanner to check the balance of the system, I do not believe there is much you will be able to do aside from checking the connections.

[turckster]

There are two communication systems in  your truck- the high speed j1939 system and the low speed j1587.  Look at it as J1939 is cable internet and j1587 is dial-up.  If you loose the j1939 to one of the ecu's--either the engine ecu or the vehicle ecu, you will get this fault.  If you loose both J1939 and J1587 then the engine will not start.

This is a PDF of the diagnostic flow chart for a 6-4 fault:

6-4 diagnostic flow chart.pdf

[R.E.D]

Thanks for the great info fellas . found the problem to be one of the two sets of cable wrapped with foil . replace it and truck running like champ now.

[Brian logsdon]

R.E.D. where did you find the j-1939 cable? My mack dealer says it's part of the whole dash harness which is hard to believe, its separate but plastic tied with the harness. I don't see why you can't purchase it separately

[Macktech689]

Keep in mind any loss of voltage or ground to the control modules will log 6-4 also. The fault isn't always in the data link wiring. Fixed a  6-4 fault this week that was caused by engine harness wires rubbing on the block causing the engine module to lose power. 

[R.E.D]

I'm reviving this old tread because I'm having this same issue with the CV.Code 6-4.

Last night I was on a job and truck started acting up.

At first it seemed like the fitting on top of the oil filter housing had rubbed  the insulation on the harness for the ecm.the fitting was kinda eaten up on one corner like if  it had been shorting against something.

I wrapped up everything in electrical tape yet issue still persist albeit less often than before.also top ecm connector had some oil . would this cause it to loose connection?

What's the best way to clean up these connectors and pins?

 

Thanks 

Red

[R.E.D]

Found the bottom ecm connector full of coolant and grime.hopefully that solves it

 

[R.E.D]

After cleaning.im getting a " no info" on the dash.could the ecm be fried?

[R.E.D]

Found the issue ..3 ecm pins have completely eroded off ..need a new ecm

[fjh]

31 minutes ago, R.E.D said:

Found the issue ..3 ecm pins have completely eroded off ..need a new ecm

Beleive there is an anti wicking harness for this issue you should invest in it!

[R.E.D]

[R.E.D]

[Mack Technician]

3 hours ago, R.E.D said:

 

What's the best way to clean up these connectors and pins?

 

Thanks 

Red

That's ugly......R.I.P. ECM

 

For future......I was given a small 5 Oz can of Deoxit D5 by Liehberr. Stuff has been my go to. Hit it with regular No Flash electrical cleaner then Deoxit and reassemble.

The machines Liehberr sold have to rotate continuous, so they are running sensitive Serial/CAN lines through a constant rotation brush style electrical connector. That Deoxit is the only stuff that would lubricate/clean/maintain a connection. Regular Dielectric grease lifted the connection stinger off the contact disc and set codes.  

Get your Coolant Level Sensor Capillary Jumper in there ASAP. I thought all trucks got a free one from Mack? Maybe someone failed to follow up? Your coolant sensor harness wire is also filled with coolant.

Edited August 28, 2019 by Mack Technician

[R.E.D]

It wasnt the coolant sensor dripping.it was the over pressure line thats connected to the pressure cap that was routed and pointing down towards the connectors

[R.E.D]

Part number seems to be a 12ms530m .there is one for sale used .local mack wants a fortune and not in stock.like always.does the new used one need to be reprogramed?

[R.E.D]

bought a used ecm ,Truck running good .have a lighting bolt code for engine brake , reckon the truck the ecm came from had engine brake.

[Mack Technician]

Be aware RED! Don’t wreck your new ECM.

What Fred is talking about is capillary bleeding through the wire. The sensor in your coolant tank ruptures internally and 10 PSI will push coolant down the wire using it as a capillary tube. That’s how coolant gets in past the seals of the J connection.

Its not likely coming from outside in, but rather inside out. You can pour coolant over the outside of your ECM all day and the seals will keep it out. The capillary failure is coming straight in via the unsealed wire. Coolant flows down the wire like a pipe.

Mack makes a jumper you install in the wire connection leaving the sensor. It’s a few inches long. The jumper has a sealing compound pressed into the wire strands. If the coolant sensor ruptures the coolant will hit the protective jumper and dead-head. 

Mack was handing out jumpers back in the day. Check to see if you have the jumper. If you don’t, install a new coolant sensor and jumper. If you do, install a new coolant sensor and jumper anyway..... cheap insurance. 

Edited August 28, 2019 by Mack Technician

[R.E.D]

Wow.! I understand stand now.will look into it.thank you every one.

Also will probably need to change the lower connector on the ecm...they are kinda corroded and were given me some pita this morning.i cleaned them out with some small picks but not real sure bout them.is it better to change cut and splice a new connector or install another harness?

[Mack Technician]

Service bulletin SB273009 coolant level anti-capillary jumper harness.

[R.E.D]

41 minutes ago, Mack Technician said:

Service bulletin SB273009 coolant level anti-capillary jumper harness.

I unplugged the coolant sensor plug and sure enough it was full of coolant

[Mack Technician]

Nice find, disappointing it took money out of your pocket. I wonder how many trucks are running without the capillary protection?

[JoeH]

Should have been a recall item.