SES light question

Tonight, I loaded my truck up with about ~500lbs. of ceramic tile. I turned on tow/haul mode, and started going down the interstate. After a couple miles, the "Service Engine Soon" light started flashing. Nothing seemed to be malfunctioning. I turned tow/haul mode off, and after a short while, the SES light went off. After I unloaded the tile and restarted the truck, the SES light did not come back on. If anyone has any ideas about this, I would greatly appreciate it.

it was flashing??? maybe the load was not heavy enough to use the tow haul mode???? just guessing but when it flashes does it have something to do with the engine internally??

Now here's some real shit... my warranty just ran out on monday.

your codes dont come up on the message center. just certain messages like battery and change oil. You have to get your codes read if you want to know what was goin on.

flash usually = misfire

Now here's some real shit... my warranty just ran out on monday.

boy that is some REAL shit, boy blender now you got me thinking about my tow mode I should test it out one day(yes my 4.3 has one :) ) before mines runs out did you use it before then if so how well did it work???

I have 35,000 miles on the truck, any idea what would cause a misfire?

Nevermind, I dunno WTF happened, but I took the truck to the 24 HR Vatozone, and they hooked up their OBDII scan tool, and it showed no errors and no logs of errors

I agree with broughy , a flash means misfire. When it flashes it means drive it as little as possible and get it looked at as soon as possible cause you could damage the cats. It will only flash while the misfire is present and if you shut off the truck with the light on, when you turn it back on usually it will not be lit up after restart unless the problem is still present. Hard to say what the misfire was caused by, imo the ignition systems on these trucks suck ass. Last fall i had a rough idle problem that took some time to solve, now it is starting to act up again a bit now and then with rough idle. Barely 1 year on new plugs and wires ffs.

Nevermind, I dunno WTF happened, but I took the truck to the 24 HR Vatozone, and they hooked up their OBDII scan tool, and it showed no errors and no logs of errors


Same thing happend to me as well last year, light came on and was flashing after the dealer messed with the plug wires and plugs but i was not going to pay them to change the plugs and wires. So i told them i would change them and bring it back to have the codes read and cleared after i changed them and there was no code stored either.

Ive used the tow haul mode quite a few times with no problems, the biggest being a load of ceramic tiles, i believe it was like 55 cases, it squatted the truck pretty good. Ive also used it towing a boat through mountains, and towing a couple of trucks on trailers. Ive had no problems with it.

Tonight, I loaded my truck up with about ~500lbs. of ceramic tile. I turned on tow/haul mode, and started going down the interstate. After a couple miles, the "Service Engine Soon" light started flashing. Nothing seemed to be malfunctioning. I turned tow/haul mode off, and after a short while, the SES light went off. After I unloaded the tile and restarted the truck, the SES light did not come back on. If anyone has any ideas about this, I would greatly appreciate it.

Since you stated that Autozone couldn't retrieve any codes, I would start by doing a voltage drop test across the grounds.
A bad ground could cause some strange thinks to happen.
I use Tow/Haul mode in my truck a lot and have had no problems.
Here is some info on Tow/Haul mode

FUNCTION


• Tow/haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR).

• Operation of tow/haul in a lightly loaded or non-loaded vehicle will not cause damage. However, there is no benefit to the selection of tow/haul when the vehicle is unloaded, this situation will cause a firm shift. The tow/haul switch is not a performance switch.

• Selection of tow/haul when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/haul is recommend only when pulling a heavy trailer or a large or heavy load.

• Examples of altered shift speeds when in tow/haul:

- Minimum 1-2 shifts pushed out approximately 13 km/h (8 mph)

- Minimum 2-3 shifts pushed out approximately 24 km/h (15 mph)

- Minimum 3-4 shifts pushed out approximately 48 km/h (30 mph)

- Tow/haul only affects shift points below 88 km/h (55 mph).

Today, I decided to use some GM Top Engine Cleaner on my truck. The stuff worked wonders and got rid of any minor pinging I was having before, which I am assuming now was due to some carbon deposits soaking up fuel. Anyway, after I let it sit for 15 minutes, and ran the engine at higher than idle rpm to blow all the crap out, the SES light started flashing again. So, I took it back to Vatozone and let them scan it again, and it said "multiple/random misfires detected" Do you think the Top Engine Cleaner cause this while it was working, or is it time for a new set of spark plug wires?

Can you feel the engine miss or just get a flashing light?
Here is a little info on missfire code.http://members.troublecodes.net/crunch/missfire.pdf
Several things can cause missfire besides ign system.
Fuel pressure or a sensor not reading right.
If you can get it on a scanner that will read what cylinders are missfiring.
If just one or two cylinders work on them cylinders . If all cylinders missfire besides ign system work on fuel system and sensor reading.
You might want to clean the maf sensor with electrical cleaner and check you ign spark out put.
Make sure it a good hot blue spark to all cylinders.
MT-2500

Today, I decided to use some GM Top Engine Cleaner on my truck. The stuff worked wonders and got rid of any minor pinging I was having before, which I am assuming now was due to some carbon deposits soaking up fuel. Anyway, after I let it sit for 15 minutes, and ran the engine at higher than idle rpm to blow all the crap out, the SES light started flashing again. So, I took it back to Vatozone and let them scan it again, and it said "multiple/random misfires detected" Do you think the Top Engine Cleaner cause this while it was working, or is it time for a new set of spark plug wires?

It was probably the cleaner causing this, but you may want to pull a plug or 2 and look at it. Alot of times these cleaners will leave a film on the plugs and cause them to misfire. I usually don't recommend this service to anyone unless they're having their plugs changed, and then I do it while the old plugs are still in it, then change them out. :2cents:


("Vatozone". That's a good one! :grinno: )