P0741 Trouble Code/Engine stumble '04/DC/SC

Long time lurker, first time poster.

I'm running into a head-scratcher on my 2004 DC SC'd Tacoma (135k miles, always SC'd). I'm dealing with some odd sporadic stumbling issues. Engine loses power and pings? at 75mph+... sometimes? No codes on that one. Possibly related to that is a the P0741 error code I've now gotten twice in ~300 miles of driving, it seems to happen when my motor stumbles so I'm assuming the computer is sensing the low RPM of the motor relative to the speed and thus triggering the Torque Converter code?

Back to the stumble/ping?

Totally hit and miss. I can drive it one day, accelerate on the freeway from 65mph to 90mph without skipping a beat. Do it a few minutes later and just about the 70-75mph mark and it will fall on its face and it sounds like it is pinging? (can't verify that as it's always combined with road noise). It won't accelerate even down hill when the symptoms are happening. Put it in neutral and it rev's right past the RPM so it is load based. Back off the throttle and it recovers as normal however push it again and it will stumble just the same. Once it starts happening, it continues to happen until I park the truck. Drive it the next day and it may or may not have the issue.

When it is stumbling, the timing retards to 0-5*, or even slightly negative.

I dealt with some APPS issues on my throttle body 3-4 years ago, throttle body was swapped and it has been 100%. Those symptoms were quite different, with that failure I was losing signal at certain pedal positions and it would return to idle and eventually error out and go in limp mode. This doesn't affect the overall accelerator function of the motor.

It has fresh plugs, clean MAF/TB. My next step is to remove and test injectors and test for fuel pressure under load. I'm actually planning to put the truck up for sale in the coming months as I've built a Land Cruiser to replace it. I want to have everything 100% before I sale it. I'd really appreciate any other insight or suggestions you might have. Thanks in advance!

 

Welcome! And subbed. I think I'm having this problem too

 

Kurt, check the main plug that goes into the transmission. I had an 05 that was throwing a few transmission codes including this one. The pins in that plug were green with corrosion. And when I unplugged it two of the pins ripped right out. Then it drove really good! Not. I wound up actually paying a friend's shop to fix it because I just couldn't get to it without a lift. But you shouldn't have that problem.

 

Great suggestion, I'll have to peak at that. It's going to sit until I'm back from the King of the Hammers event, when I get back and caught up I'm hoping to tear into everything.

 

Anyone emailed Gadget?

 

I have not personally, I don't know him well enough to reach out to him. If anyone does, I'd appreciate it



I've not had a chance to do anything on the Tacoma, it has been sitting in the shop while I was at the King of the Hammers event chasing for a team running in the Every Man Challenge. With that behind me I'm planning to start serious troubleshooting this week. Any other advice or ideas would be appreciated. Thanks!

 

The plot thickens...

Drove it for a quick drive last night to pick up some parts. Ran great, no stutter or check engine light. That is until I exited the freeway, as I came off the off-ramp the trans temp light illuminated. I was back on surface streets and driving slowly, turned off in a minute or so. Did it again on may way home, again as I pulled off the off-ramp. Still haven't had a chance to put it in the shop, hoping to get a chance this week... too many Cruisers in the way

 

The plot thickens... more.

Finally had a chance to pull the Tacoma into the shop yesterday. We started by dropping the transmission pan and inspecting the filter (screen) and overall condition of fluid. The fluid was definitely darker than it should, likely the sign of heat but it was free of metal debris and it wasn't the worst fluid I've encountered. The screen did have a bit of 'gunk' in the mesh but it wasn't super bad. We pulled the SL solenoid from the transmission following the P0741 code that activated. It shows a quick testing procedure for solenoid using air. Here is where I'm stumped. It clearly shows that you run air into the o-ring side of the solenoid and it should not let any air through until you apply 12V at which point it should. I thought I had struck gold as mine let's air through with 0 power however when I apply power it blocks (closes) the solenoid. Exactly the opposite as I read it in the FSM diagram. OK, so I order the solenoid from Toyota and amazingly they have it in stock (over $200 ), before I install it I quickly test it using the same procedure as the FSM calls for. It is identical in function as my old one... which is opposite as the FSM calls for.

I've attached the FSM P0741 PDF, am I up in the night and reading this wrong?

 

I've made a little progress. I was able to confirm with a Toyota tech that the solenoid is operating as designed, he said it isn't super uncommon to run across minor errors like that in the FSM and this was likely one of them. He has offered to come inspect my valve body one evening this week so I'm anxious to get his take on it. At this point I'm looking at either a valve body replacement or a torque converter.

While the trans has been opened up I decided it was the ideal time to get some things done under the hood. We pulled the supercharger and replaced the fluid in the nosecone. With the injector off I had access to the injectors so I went ahead and pulled those and had them cleaned and flow tested. We buttoned that all back together last night but have not been able to fire it yet as the trans is till sans pan.

Fingers crossed Will (the Toyota tech guru) can come diagnose the trans issue for me

 

P0741
Torque Converter Clutch Circuit Performance or Stuck Off

 

Yessir, I posted a link to the FSM diagnostics above.

I've since pulled the trans and the torque converter go dropped off today for an overhaul. By all accounts that should do the trick.

 

Update: As the solenoid operation 100% matched that of the new solenoid albeit opposite of the FSM, and my valve body checked out so we pulled the torque converter and had it rebuilt with beefed up friction material. Buttoned it back up yesterday and gave it a quick test drive, so far so good but I've not had a chance to get it on the freeway in a lockup condition just yet.

 

Alight, update of sorts. While I had the supercharger off for the nosecone oil change, I pulled the injectors and had them cleaned and balanced, the cost wasn't much and it was worth the piece of mind knowing they have a clean bill of health and a long life of trouble free service ahead of them. We cleaned the MAF and throttle body and verified all the connections were clean. We dropped the trans and took the torque converter to be rebuild (Tip Top Trans in Salt Lake City cut it open while I stood there). The friction pads were definitely worn, not 100% gone but definitely showing wear. They relined the friction material with an upgraded pad and had it ready for me the next day. Re-installed the trans and topped off the fluid. I took it for a few spins around the surface streets yesterday, running strong, shifting strong, no CEL and no engine stumble, however I previously hadn't experience any issues unless I was 75mph+. So, fast forward to today... I installed a fuel pressure gauge so that I could take it for a good stretch on the interstate and watch my fuel pressure if/when the stumble occurred. Sure enough at times the pinging? noise and associated stumble was back in the 75-80 range however nowhere near as bad as it was previously and it was very isolated, i.e. it did it on the relatively flat interstate but not as I really pushed it harder up and over a steep canyon (Parley's for those familiar). I've ruled out fuel pressure issue as it stayed 35-45psi under all running conditions including the stumble scenario. Odd. I flipped around at the junction and started down Parley's, engine was running cool and I was cruising at 70'ish when the CEL popped back on with the P0741 code. Bummer. I'm 0/2 on my issues here.

I'm still wondering if the two issues are somehow related, i.e the stumble confuses the trans as it has a known engine speed relative to the vehicle speed and the gear it is in? Going off of the FSM I've ruled out the solenoid, ruled out the torque converter so that leaves me with only the valve body to replace. So, who has replaced their valve body and what did you replace it with?

 

Assuming the two issues (trans CEL and stumble) are in fact two different issues. Is it possible the knock sensor is picking up some 'noise' from perhaps the Supercharger and thus retarding the timing thus causing the 'stumble' I feel. I have in fact verified that when it is stumbling, the timing retards to single digit numbers. Anyone had a knock sensor fail without firing a CEL for the sensor failure?

 

Update of sorts. Right before I departed for Aus I dropped my truck off with an old friend, Joey @ Tip Top Trans in SLC. He drove it around for a bit with his diagnostic computer and verified the trans wasn't locking up despite having a fresh torque converter. Either the valve body or the solenoids and given the solenoids tested OK, he suspected the valve body. One of my shop hands (Olly) had a spare A340 kicking around so he dropped it off at Tip-Top and Joey swapped it out and drove the truck for another week before giving it a clean bill of health. I've only put ~200 miles on it since I've been back from Aus but so far, so good, no returning code. Fingers crossed.

However, the slight engine miss/ping under full load is still there. Likely not even noticeable if I were not pointing it out but it is still there. Need to start troubleshooting that again, perhaps the knock sensor mod is in order.

 

So my 3.4 tacoma threw me this p0741
I thought on switching my converter but with your problem it got me thinking what if it not even that. Did the the valve body fix the issue? I have the same problem atm and around the same speed 73-80 i feel the truck looses power at times and that ping i hear that aswell im very curious on how your truck turned out.