bziggy

Hello I need help I can't get tow/haul to engage light up on the dash. The light is working beacuse I did the test were you hold the trip button and turn the key on and it goes through the test of every thing on the dash. I also checked the switch and it to is working. Went through all the wiring and it's all good. The trans shifts find and no other problems but the tow/haul will not light up and work. Anyone know how it works or what would cause it. It just stopped working the other day. Thank you.

.boB

That usually means a control module has failed.

bziggy

What control module ? I was thinking it was the od selenoid on the valve body. This is the only thing I can think of it being. Everything eles works fine it shifts and locks up with out any issues just can not get tow/haul to light up and work.

no_6_oh_no

I assume from your description OD still works fine. Does the TH functionality work at all when you push the button?

steelblitzkrieg

This may be a dumb question, but didn't the 05's only have OD and OD off?

Has the T/H light ever came on before?

It wouldn't surprise me if the T/H indicator was there for future use as in 2006 model?

no_6_oh_no

The 05's do NOT have an OD off, its TH only. Irregardless, the light should come on when the button is pushed.

steelblitzkrieg

Okay, so 06 added OD-off.

no_6_oh_no

Yep, 06 had OD Off like the 04.5 and earlier trucks, plus, a true TH like the 05's.

bziggy

The OD works fine have 4th gear and lock up. The tow
haul is not lighting up and yes the light works and the button is good. I worked fine and just one day stopped working. Can't find anything out side the trans so i am assuming it inside.

TonyB

Sounds like it's the wiring between the T/H switch and the Trans/ECM.

Sorry I can't be more specific than that.

Tony

no_6_oh_no

Ther eis nothing inside the trans that controls that light or TH. The TCM controls the trans with its shift algorithms.

It could be the ECU, the button, the cluster, or a bad connection on the bus.

When you hit the button does your shifting and lockup change to TH or does it stay the same?

If you get no shifting changes the problem is between the button and the TCM and the TH is not activating. If the shifting changes but no light its generally a cluster problem.

bziggy

The light is working I did a test for the cluster and it works. The shift dose not change at all. I am being told it's in the trans and it's the overdrive / TQ lock up solenoid in he trans. It's the main round plus that is in the top of the trans. I am being told it's bad and that is why no light or change in shif pattern. Trans shifts fine just no tow/haul light or change in shif pattern.

no_6_oh_no

Ok, first the cluster test is just to verify the gauges and lights all work. It tells you nothing baout the true operation of the system. The light works that means the cluster is not getting a signal from the ECU to light the TH indicator.

First step, clean ALL the battery connections and grounds and verify the batteries are good. Also check the under dash ground and make sure it is clean and tight.

The next step is to verify the momentary button on the shift lever is actually notifying the ECU to switch to TH. Has that been done becuase a lot of the failures are just the button bad.

Are you getting codes that suggest the the solenoids are bad? These solenoids rarely go bad, more often than not its a bad connection causing the issue.

Since you still have OD and lockup how is it possible the solenoids are bad? Causing a light that is not connected in any way to the trans to fail to light? If you have codes the its possible you have a bad plug or its contaminated with trans fluid and needs replaced. If not, run don't walk away from whhomever is telling you the solenoids are bad cuz they are guessing big time.

ramman

The switch gives the ECM a ground pulse to trigger the tow haul modes.

bziggy

Ok thank u guys for all the help. So I checked with a volt ohm meter and the switch is open till you push it the closes. When you let go the switch goes back to open again so it is working when back through all the wiring in the truck and can't find anything wrong. No broken wires good ground on everything. The main plug to the trans the round one on the top of the trans if wet with trans fluid. I dry it but trans fluid keeps showing up on it. Not a lot just wet though. This is the plug that is for the OD and TQ lock up solenoid. The one I am being told is bad. I have a few P codes P0336 two times P0338 P0713 P0868 P2769. They seem to be for voltage high and low at diffrent things. I should be able to engage the Tow/haul when I hook up to the obd2 with a scan tool I thought but it still will not work. I bought the solenoid and am thinking of putting it in. I am unsure as to what to do since I can't find anything wrong.