Egr fault mass flow to high

[mdixon]

So I've got a 2012 CXU613 489k miles that I'm at a loss over. A month ago this truck rolls in with egr mass flow too high, won't complete a regen. I replaced the egr valve after testing, weak return spring. Code clears, return to service. 2 weeks later its back, same code. Dpf at 150% soot. Inspection of dpf shows high backpressure and a Crack in the dpf outlet, full of crystallized def. Replaced parts, cleaned dpf, run regen. Regen kicks out in 10 minutes, low temp. I replaced the 7th injector and the fuel/air lines, changed filter dryer cartridge that was saturated. Run regen, fails. Soot level goes down 20% and temps got the 850. Run diag on the vgt actuator, that sticks in the open position. Replaced vgt actuator, Run regen. Regen temps hit 930, then 12 minutes in it kicks out. Now I start another regen, and look at the egr info, my egr dp is jumping up, temps going into -°. Chase wiring, all clear, no shorts, broken, high resistance, nothing. I'm at a loss here, about to send the truck to mack because as far as I can tell it needs an ECM

 

Any suggestions?

[Onyx610]

The only other thing I could think of would an AHI module. Usually you would get a code for that. You may be right on a eecu. Curious to what you find out. Hopefully someone can help you. 

[mdixon]

Fuel pressure shows within 3psi on both sensors, and the 7th injector isn't maxing duty cycle before cutout. I may have to put a gauge on to verify though. We're probably going to rts the truck and see what pops up for faults again. 

[Onyx610]

I’ll see if I can find any info on this as I don’t have my username and password written down at home. 

[Onyx610]

Here’s some info on the dosing block. 
 

https://static.nhtsa.gov/odi/tsbs/2022/MC-10209717-0001.pdf

Edited December 28, 2022 by Onyx610
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[mdixon]

1 hour ago, Onyx610 said:

Here’s some info on the dosing block. 
 

https://static.nhtsa.gov/odi/tsbs/2022/MC-10209717-0001.pdf

Got 1 for us10, or is it the same procedure? I already changed the injector, it was clogged with rust from the air line. 

[Onyx610]

Same thing, I’ll see what I can find tomorrow for your truck. Usually bad air dryer will destroy those ahi modules. You seem to do nice diagnostics so I believe your close if not pin pointed to eecu. 

[mdixon]

Is there a module between the pump and the injector on the diffuser pipe? Looks like a banjo fitting down behind the fuel filter with a pressure sensor.

[Onyx610]

There’s a fuel pressure sensor on the “module” but nothing like that in between. I’m trying to think of this sensor. Hopefully Mackpro or vmac3 sees this, they would be a lot more helpful than me. 

[Mackpro]

Put a 1/4” air line Tee in the air line going to the AHI . Hook a good air pressure gauge to the Tee . Start regen and during regen it should be right at around 31-33 psi. This is very important. Not changing the air dryer filter causes the regulator to the AHI to fail and cause failed regens. 

[mdixon]

25 minutes ago, Mackpro said:

Put a 1/4” air line Tee in the air line going to the AHI . Hook a good air pressure gauge to the Tee . Start regen and during regen it should be right at around 31-33 psi. This is very important. Not changing the air dryer filter causes the regulator to the AHI to fail and cause failed regens. 

All that is brandy new. I cleaned the air lines back the frame manifold, and replaced the steel one behind the head. Regulator and solenoid work and makes 30# when commaded on, no air leaks. New 2 way check tee on the 7th injector. Brand new filter dryer cartridge and valve. I do all that whenever I find debris in the tee screen. 

[Mackpro]

For AHI stuck closed or stuck open fault code . We would start with flow testing the 7th injector and replace it if not in specs. Hardly anyone outside of dealers have the flow testing kit  so replacement is the normal routine. Remember there are 3 and now possibly 4 different 7th injectors on Mack’s /Volvo engines now. Testing the air to the AHI as I mentioned above and replacement of the air drier filter are  must . The air pressure regulator for the AHI is usually mounted on the bracket the air drier is on . 

[Mackpro]

1 minute ago, mdixon said:

All that is brandy new. I cleaned the air lines back the frame manifold, and replaced the steel one behind the head. Regulator and solenoid work and makes 30# when commaded on, no air leaks. New 2 way check tee on the 7th injector. Brand new filter dryer cartridge and valve. I do all that whenever I find debris in the tee screen. 

Oh . So you have the early big 7th injector with the coolant lines ? 

[mdixon]

Problem originally presented as egr flow too high. I wasn't satisfied with regen quality, NO REGEN RELATED CODES HAVE APPEARED AT ANY TIME. Only achieving a 20% decrease in soot level during forced regen is not good, and what led me down this path

[mdixon]

1 minute ago, Mackpro said:

Oh . So you have the early big 7th injector with the coolant lines ? 

Correct, 2012 first year with the scr

[Mackpro]

Can you view the DPF differential pressure during regen? 

[mdixon]

Only if i unplug my scanner and re connect after initiation. Thats what i did today, im getting spikes in that reading, as well as non plausible temp readings in the egr. Happening KOEO too. Checked the harness for oil contamination but all dry at the EECM. I really think there's a controller short

[Onyx610]

He’s not using PTT by the way

[mdixon]

Oh yeah lol. BOSCH ESI TRUCK is my scan tool. It's pretty good, but definitely lacks the capability of PTT. 

 

I did try and verify the spikes through my multimeter and breakout leads, but voltages were constant in the dp sensor, no ohm spikes in the temp side.

[Mackpro]

I just went down this same road with a 2012 Volvo D13 last week. Started with EGR flow codes. Updated to the newest EGR differential sensor and venturie pipe. It’s a kit that comes with everything you need. After doing this the EGR codes went away but the failed EGR diff sensor caused EGR valve to stay open more than it should and caused over sooting of the DPF filter. So I started a regen and couldn’t get the center T2 DPF temp over 750. Borrowed a flow  tester and 7th injector had really low flow . Started at 2 LPM ( liter per minute) flow , cleaned and re-tested and had 3 LPM . Spec is 4-8 LPM at 30psi . So replace the 7th injector ( no fun on the big ones, a super thin 7/8” wrench is a must) . Started a regen and temps slowly and I mean super slowly got to 880 after about 25 minutes. The DPF differential pressure was around  .8psi  and slowly dropping to about .5 psi at end of regen. Usually the regen temps shoot up pretty quickly on the T2 when the fuel starts dosing. To make it right I finally had to pull the filter and have it cleaned and went ahead and had the top part ( catalyst) cleaned too. After that the temps rose quickly and my DPF differential pressure only got to .3 psi at it’s highest. 

Edited December 29, 2022 by Mackpro

[Onyx610]

What is a glow tester? 

[Onyx610]

Oh flow tester lol

[Mackpro]

If your having EGR temp sensor readings that are erratic. I believe there is a service bulletin on the pins in the harness causing faults. I’ll see if I can find it . 

[Mackpro]

2 minutes ago, Onyx610 said:

Oh flow tester lol

Lol , your right .  I corrected it . 

[Onyx610]

1 minute ago, Mackpro said:

If your having EGR temp sensor readings that are erratic. I believe there is a service bulletin on the pins in the harness causing faults. I’ll see if I can find it . 

Yea, if they are going into the negatives I think that’s a good place to start. Just odd he’s not seeing any fault codes.