affmondo22

I just finished my headgasket a couple weeks ago and the truck has been driving fine.. its a little sluggish and slow, but then again, its a 3.0.. Well the check engine light comes on today and i pull the code, and theres 3 of them, says the tps, o2 sensor, and the intake temp sensor were all found to have an open circuit for .5 sec or longer. My question is, does anyone know where i can find wiring diagrams for these components? or does anyone know if they share a common ground point or something? they are all connected, so im assuming a ground problem?

affmondo22

anyone? im starting to think they ground in the ecm.. any help at all would be appreciated..

4Crawler

iTrader: (3)

A Factory Service Manual would have the wirig diagram for the engine and ECU.

abecedarian

if it was a ground point, you should also get a code for the afm along with the intake temp sensor. I'd look for any pinched part of the harness that may be causing the wires to short, or for loose or wet plugs.

affmondo22

I checked the online fsm for diagrams, but could not find any, i wish i still had access to alldata. It is throwing a code for the intake temp sensor, but not the afm. I have checked the wires that i can see, and they are not pinched, but i am kind of hesitant to tear it apart again because i just got it back together. Do you know where this ground point is?

abecedarian

The TPS doesn't 'ground' anywhere external to the ecu.
The O2 sensors both have ground but it is part of the heater circuit, not a signal wire and the diagram doesn't state where it lands other than there are several other grounds connected with it.
The AFM has a single 'brown' ground wire and the diagram doesn't show where it grounds at, but likely near the ecu. And the ground appears to only close the Circuit Opening Relay to turn the fuel pump on.

I'd suggest breaking out a multimeter and checking for continuity in the harness from the sensors back through to the ECU.

Also, can you post what the actual codes you read are?

affmondo22

the actual codes were dtc codes 21, 24, and 41

so it looks like ive got a lot of chasing wires ahead of me.. the only thing im wondering is why they all went at the same time.. they have to share a common splice or something in their circuits. The code stated the circuits were found to be open

thanks for all the help so far abe, i hope you dont get impatient with me

abecedarian

I don't get aggravated easily.
Knowing the codes changes things as now it gives me some ideas for suggestions. As you'll see, the components themselves could be the issue. I'd rather you spend a few hours testing things that are fairly easily tested than hear about you pulling your hair (or driving the truck off a cliff) over tracing wires down only to find the wires are fine. Unfortunately, some of these things are expensive to replace but at least you'll know if they're good or not. At which time you'll need to check the wiring and if that's all good, it may be new ECU time. Having a friend or other source willing to let you swap the ECU, if it comes to it, would help.

One thing I forgot to suggest is disconnect the battery for a few minutes to clear the ECU. Verify you have no codes, then go driving and see if they come back.

code 21 is either: (1) Open or short in heater circuit of heated oxygen sensor for .5 seconds or more; or (2) At less than 60 miles per hour while engine rpm's above 1500, amplitude of O2 sensor is reduced to between .35 and .7 vdc continuously for 60 seconds or more. This implies the O2 sensor is not maintaining proper operating temperature. The O2 sensor plugs have 4 wires of which one should be brown and the other white/red stripe. You should be (truck side, not sensor side) continuous to ground on the brown wire and the white/red should have +12v. If that is true, the O2 sensor(s) may be bad.
***you have to check the voltages with the truck running*** this may throw another code.
Additionally, you may have 2 oxygen sensors and the code does not differentiate between the two so you may have to test two sensors and plugs.

code 24 is open or short in intake air temp sensor circuit. Could be a problem with the wiring or could be the sensor in the AFM is faulty. You can check the AFM with the guide here: http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml. In particular this section: http://www.4crawler.com/4x4/CheapTri...tml#AFMtesting. You'll be concerned with the E2-THA resistance.

code 41 is open or short in TPS signal or IDL contacts are closed when the output is greater than 1.45v. Could be a faulty throttle position sensor. You can use the guide here: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml to check it.

affmondo22

thank you so much.. i cant really do much about this right now, as i am at work,but first thing tomorrow i will get to some testing

abecedarian

don't forget to thank 4Crawler for getting the write-ups I suggested using above for the AFM and TPS.

keep us informed.

affmondo22

oh i will.. i reset the light while i was at work, and i drove around all night with it. The check engine light never came back on, but it took 2 weeks to come on after i did the headgasket, so ill give it more time.. I dont see this turning out too good for me.. but at least it doesnt burn coolant anymore!

affmondo22

and thanks for detailed writeups 4crawler, although i shoulda mentioned i have a 3.0.. it says in the articles that most of it applies to other toyota efi engines

thook

I think it's highly unlikely any of the components themselves are bad considering they were fine (I'm assuming, anyway) before the HG r/r and even to go bad all at once. Not that it would hurt to check them, but a vehicle generally just being "sluggish" doesn't sound like those components really being bad. Usually I've found it's a wiring or ECU issue. What Abe said about testing at the ECU terminals is a good idea, I think.

http://personal.utulsa.edu/~nathan-b...e/102engin.pdf

Also, in conversations I've had with the head tech at the local dealer on other issues not too far removed from your topic, he'd mentioned problems they'd run into by mechanics not having reinstalled the ground wires to the heads, engine block and body on HG recalls. Something worth checking.

On the other hand......did you ever once turn the key to ignition before hooking those components back up?

abecedarian

oh thook, yer so cute...
I said

thook

I'm aware of that. But, maybe he wasn't aware of why you'd suggested doing so?

affmondo22

you know what thook... you might be on to something.. because the first time i was ready to crank my engine, it turned out i didnt have the major banjo fitting tight enough and it leaked a bunch of gas.. so in order to tell where it came from, i turned the ignition when the intake manifold was ready to come off.. so that could've done it for two of the components.. but that doesnt explain the o2 sensor, unless thats an old code that wasnt erased properly? Also, im gettting 13 miles to the gallon, and i dont know if thats related to the code or if its because i am almost constantly in 4wd due to snow and letting my car warm up before i go anywhere

thook

Well, how is the truck running? Notice any strong exhaust?

affmondo22

the trucks running good.. its running just like it was before the headgasket went.. what do you mean by strong exhaust? I'll have to watch for that, i havent been paying much attention to my exhaust

thook

Strong exhaust as if it was running too rich. But, if the motor is running good, that would indicate to me that the fuel mix is okay....not too rich or too lean.

Any updates, btw?

affmondo22

It does smell a little rich but it's running real good. The light never came back on either. I'm going to hook the timing light back up to make sure my timing is on because I've heard you have to jump two terminals when you do it? I'm gonna look into that because someone suggested that could be causing my poor gas mileage