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Flashing check engine when towing

O

OhmsLaw43

PM 2017
Full Member
Joined
Jul 9, 2016
Messages
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I have a 2005 Avalanche that had gone through 4 transmissions.  I installed a Super cooler transmission cooler and a temp gauge but transmissions kept going out.  I had replaced the oil pump and cam (along with all the lifters) along with the intake manifold and gaskets.  I never had the issue I have until I replaced the 3:42 gears with 4:10 posi.  Now, when towing, everything is fine until I let off the gas going downhill.  I get a flashing check engine that goes away once I press on the gas again and then doesn't show up until after another hill and letting off the gas.  When not towing I never see a check engine at all.  I do have a CAI and a Vortex spacer (don't know if it does any good but what the hey).  I also have a default Diablo predator HP tune in the truck.  Stock exhaust and wheels as well.  Anyone ever seen this??
 
Did you have the truck reprogrammed when you put in the 4.10. Also get your codes read.
 
What is the code?
Flashing Check engine means MAJOR MISFIRE and you wull ruin cats if you continue on.
 
I have a code reader so I'll be checking the historical codes tonight.  I had it already programmed before switching to the 4:10's  It just seems odd that it would have a misfire when deaccelerating in tow mode and towing but is fine when I'm not towing.
 
OhmsLaw43 said:
I have a 2005 Avalanche that had gone through 4 transmissions.  I installed a Super cooler transmission cooler and a temp gauge but transmissions kept going out.  I had replaced the oil pump and cam (along with all the lifters) along with the intake manifold and gaskets.  I never had the issue I have until I replaced the 3:42 gears with 4:10 posi.  Now, when towing, everything is fine until I let off the gas going downhill.  I get a flashing check engine that goes away once I press on the gas again and then doesn't show up until after another hill and letting off the gas.  When not towing I never see a check engine at all.  I do have a CAI and a Vortex spacer (don't know if it does any good but what the hey).  I also have a default Diablo predator HP tune in the truck.  Stock exhaust and wheels as well.  Anyone ever seen this??
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That part right there shocks me. What are you towing that you would have gone through 4 trannys??? How many miles on each were they rebuilt properly? 
 
The original gave up the ghost around 65k miles.  I bought the truck with 49K on it and it was a fleet truck before I bought it.  Pretty much rode hard and put away wet.  The second one died of heat exhaustion so I put a Super Cooler and a transmission temp gauge in.  The third one, the aftermarket TC let go.  This one has lasted forever with no issues at all.  I'm stumped by the whole towing equals flashing CEL and not towing equals no CEL.
 
Ok, code is the so informational P0300 (random misfire).  I reset the predator map to the less aggressive 87 octane HP one vice the DiabloTune and checked all the ignition wires. Plugs only have less than 50k on them so I figure they should be good
 
How much weight are you pulling and are you pulling in "tow" mode?

Air filter is in good condition?

Assuming engine temp is not rising at all?

Two things I would suggest you check is your fuel pressure and check your plug wires for cuts or black marks. You can also try running your truck in the dark and look for arcing near the plug wires.

You could have an issue with the fuel system that shows its self when you drop from a high load to a low load.

I am assuming you used a torque wrench and used proper sequence when reinstalling intake and used a felpro or at least a new version of the OEM gasket.

If you are running a K&N style oiled filter I would suggest cleaning the MAF sensor and cleaning the TB. Make sure you clean these properly as they can be damaged if done improperly.  The oil on the oil impregnanted filters can go into the air when the filter is newly oiled causing issues with the readings the MAF sensor gets or gum up the TB. I only mention this because you said you had a CAI and the issue happens when you go from a high load mode to a low load.

Shooting in the dark mostly trying to give you some ideas of things to try.

Rodney
 
redheadedrod said:
How much weight are you pulling and are you pulling in "tow" mode?  I'm pulling around 4,500 lbs. and yes I'm in "Tow Mode" in 3rd gear.

Air filter is in good condition?  I just cleaned, re-oiled (lightly) and installed a Spectre filter on the CAI

Assuming engine temp is not rising at all?  No, engine temp stays the same

Two things I would suggest you check is your fuel pressure and check your plug wires for cuts or black marks. You can also try running your truck in the dark and look for arcing near the plug wires.

You could have an issue with the fuel system that shows its self when you drop from a high load to a low load.

I am assuming you used a torque wrench and used proper sequence when reinstalling intake and used a felpro or at least a new version of the OEM gasket.

If you are running a K&N style oiled filter I would suggest cleaning the MAF sensor and cleaning the TB. Make sure you clean these properly as they can be damaged if done improperly.  The oil on the oil impregnanted filters can go into the air when the filter is newly oiled causing issues with the readings the MAF sensor gets or gum up the TB. I only mention this because you said you had a CAI and the issue happens when you go from a high load mode to a low load. That's my next thing to try.

Shooting in the dark mostly trying to give you some ideas of things to try.

Rodney
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I just had the 4L60e in my blazer repaired again after torque converter and 3-4 clutches failed.  It was setting occasional intermittent P0300 misfire codes apparently because of the trans/torque converter.  Trans is fixed now and false misfire codes are gone.  

With yours, sounds like it shifts to 4th and TCC engages when going downhill and that is when a false misfire is set.  Are you familiar with 4L60e evolution, PWM, and ECCC operation of the Torque Converter Clutch?  You have to have the right torque converter in a trans with both PWM and ECCC (and you have both in a 2005 Avalanche.  One part does not fit all, and a lot of rebuilders try to disable the ECCC and put in converters with older friction materials.  For ECCC operation you need a converter that will handle a slight amount of constant slip by use of carbon fiber friction materials in the torque converter.  Otherwise it will fail, and I bet your trans is on it's way out again.

The difference with towing is that you will not be in OD with TCC engaged unless you are on an easy grade or coasting with foot off the brake.  I bet your trans is on its way out again, and it is the cause of a false P0300.  The difference with 3.43 vs 4.10 is with the steeper gears your engine is trying to do more braking of the entire rig and remember this involves your trans and torque converter with the converter locked up as much as the ECCC will allow.

But this is only an opinion on the Internet and you know how those are...................

http://www.sonnax.com/tech_resources/214-20-years-later-what-s-new-with-4l60-e-pwm-modifications

http://www.sonnax.com/tech_resources/254-a-slippery-slope-the-what-and-why-of-woven-carbon
 
I hope you're wrong about the transmission.  I tow in 3rd so it isn't trying to go to 4th or OD.  I changed the map in it to see if that helps along with cleaning the MAF.  If it still does it then I might resort to other t/s steps (putting it in neutral downhill, shifting up to drive, disengaging the tow mode, stock map) to name a few.  I also went to a very good transmission shop who used a factory (GM) 2005 torque convertor and didn't modify anything by way of the TCC.  I could change all that with my Predator but do not want to go that route as I'm not that familiar with the different settings and how they would affect the transmission.  Normal driving is zero problem with no error codes ever.
 
Why wouldn't you use over drive when towing?

I know before the "tow" switch you were supposed to tow in 3rd but my understanding was that with the advent of the "tow" switch this became unnecessary and you should always tow in Drive.

My understanding is in prior vehicles in Odrive it reduced the amount of fluid traveling through the transmission so it cools less and if towing in Odrive you were more likely to get into a situation where the torque convertor would continuously lock/unlock causing heating issues.

Someone please correct me if I am wrong... And you can prove it... ;)

Rodney
 
Except I was wrong  ;-(  Turns out you can drive in "D" however, most of my towing is in very hilly country so 3rd and tow mode are suggested.  I'm wondering if I take it out of two mode going down hill if the CEL would stop flashing.
 
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