Electrical help

[cuel]

I'm trying to help another member here(Dragk913) with his idle issues in my spare time(which isn't much). 90 N/A Auto.
No vacuum leaks, smoke tested to make sure. I tested the ISC, and it works. I checked for power, and its getting 12v. to the 2 middle pins. It seems that it isn't getting a ground signal to the other 4 pins to operate the motor. Not really sure how to test for ground pulses. I think they would be to fast for a test light, but maybe I could use a noid light instead? I actually used the test procedure to set the ISC with the car running(harness dis-connected) so that it would idle decent. If I'm reading the diagram correctly, EO1 and EO2 are the ground for the ecu. Are those the grounds that bolt to the intake? I've already been through all the grounds in the engine compartment, and they're all in good shape. I know I'm missing something....

Any help would be greatly appreciated

C.J.

 

[jetjock]

You can test for ground side switching by connecting one probe to battery positive or to pin 2 or 5 on the valve. Same difference as long as the Main EFI relay is closed. Test light should show something but an led would be better. I keep tellin ya, order a Power Probe

Be sure the IDL contact is closed in the TPS (no code 51 with throttle closed) because without it the ISC system will be disabled.

Does the valve step open on engine shutdown? No IDL closure needed for that but you should still check for it. Is idle high when cold and gradually fall? PS idle up valve OK? Dashpot? Is the throttle fully closed?

 

[cuel]

Thanks JJ, I was hoping you'd reply.

I thought it might be the TPS when he first brought it to me, and set it according to the TSRM specs, and cleared the code. I'll check for codes again tomorrow. The valve does not step closed when the engine is shutdown. As far as I know, the idle stays where I set it, whether cold or warm(he brings the car in the afternoon, I need to get him to leave it with me for a couple days). I shut the car off, let it sit for about 15 min., then started it again. It should have idled up for a few minutes, then stabilized at a normal warm idle. Instead, it started and immediately idled where I had set it. The ps idle up valve... I need to check that. Dashpot works, and I set the throttle linkage when the engine was installed. I've cleaned the throttle body to be sure there wasn't any gunk holing it open. Yeah, I really do need to order that Power Probe(i'll get one this weekend).... My noids are led's, so I'll try those tomorrow.

Thanks again,
C.J.

 

[jetjock]

Yeah, sounds like it's not working. The valve should step full open a few seconds after the engine is stopped and the main EFI relay will de-engerize just after that. Make sure the main relay isn't going off with the key. It's ECU controlled and should wait until the ISCV is done. The only way the relay would go off with the key is the ECU is bad or the wiring to it has been jacked. The TPS doesn't matter for the shutdown sequence.

Anyway, focus on getting the valve to step open on shutdown first and go from there. You said dummying the valve worked so it must be good. I dunno. If the valve has + power on the two pins (measure there to see if the main relay is staying on) the only thing left is the ground side wiring or ECU. Let us know what you find and shoot me a PM if you need something.

 

[cuel]

Cool, thanks Jet.

 

[Dragk913]

Woot! Go C.J.!

Thanks Jet!

 

[Kckazdude]

Just for a future reference, I use the SST test light for a lot of my power/ground switching tests.

 

[cuel]

I figured it out. The tps was bad. I had checked it 2 weeks ago, and had a 51. Figured it wasn't set right after they put the motor together, so I set it according to the tsrm, cleared the codes, and sent him home. Had Austin check for codes a couple days later, and none were there. Checked it yesterday, had a code 51 again, so I tested the tps, and it failed. Couldn't get it to calibrate correctly, either. Put a new one in today, and reset the ecu. Took it for a 20 min. drive, and no codes came back. Had him pick it up today, and bring it back Sat. for me to check for some other misc. problems. I'll check for codes again just to be sure.

 

[jetjock]

No kidding. So the idle valve steps back now? That's odd because the TPS doesn't matter for the shutdown sequence. I'll have to look into that some more.

Fyi, be careful testing the VTA portion of a TPS using the resistance values in the TRSM when it's not installed on the TB with the throttle stop screw set because if you read carefully the book procedure assumes it is. Some will read slightly low when zeroed off the TB, low enough to trigger a code 41. It's the reason you can't just plug any TPS into the harness without getting the code even if the TPS is functional. They can still be used even if the code remains after calibration but you have to set them up a little differently than the book says. Either that or fudge the lower stop inside them. I've seen more than one good TPS rejected because of this. They've always been non-OEM parts though.

it's just another reason to use volts instead of ohms when doing stuff.

 

[cuel]

Thanks for all the help, Jet, I really appreciate it.

No need to look into it any further. The ISC steps back so quietly I couldn't hear it without a stethoscope. Even then it was faint, but it stepped 3 times. Is it supposed to be that quiet? I can hear mine easily with the hood open.
The ISC works on start up now, though, where it wasn't yesterday. That's what made me get the stethoscope out. I thought I had 2 separate issues, and only had one.
I had the original tps installed when I tested it(coulda kicked myself for not checking the codes again before posting originally). I got an OEM Toyota tps for it. I've noticed that most tps sensors have to be turned back slightly to install them on the t.b., then turned forward to the correct position. They don't seem to have the same resting position installed as they do off the t.b. I always test them installed to be sure that I'm getting the same signal as the ecu.

I had him drop the car off yesterday morning, and was able to take the afternoon to work on it. Helps when I can dedicate the necessary time to correctly diagnose the problem. Thanks for pointing me back in the right direction as well

 

[jetjock]

It's either very quiet or you're going deaf .

I can't hear mine with the hood closed but it's noticeable with the hood open. As I said it'll do that no matter where the throttle is. When the engine is running it's a different story. IDL going open will kill the ISC system. Can't have the valve trying to control idle when driving around you know. It also effects ignition timing.

You're right about the TPS not being on it's internal stop when installed. The TCCS judges VTA to be bad when it's above 4.8 volts or below 100 mv. Those levels are set by a resistor in the ECU to detect when the input becomes open or shorted. If you look at the test procedure in the TRSM you'll see it specs a minimum resistance on VTA with the throttle plate closed and the throttle stop screw set. In other words the book specs are for when the TPS is *on* the TB.

The problem is when a TPS is off the TB and against it's internal stop that resistance can be lower, low enough to drive the input below 100 mv and trigger a 41. Once it's on the TB and set right the resistance should change enough to generate more than the 100 mv minimum. Not all sensors do it but I've seen people struggle with a 41 because of this, by trying to "test" a TPS on the harness without installing it on the TB.

If a TPS is going to be tested off the TB the actuator should be rotated off it's stop an 1/8" or so to see if the 41 clears. Alternately the resistance or voltage on VTA can be checked. If it comes up (and the IDL contact also checks out) the sensor is good to go and can be installed on the TB.

Anyway, nice job. The guy is lucky to have you at his disposal.

 

[cuel]

Thanks Over 90% of what I usually work on is OBD2, so I can look at everything every sensor is doing as I manipulate the vehicle. It makes diagnosing bad sensors much easier. But that's a subject for a different thread...

 

[cuel]

Voltage tested the tps on the afore mentioned vehicle. Used the + contact on the tps, and the - contact on the batt. ground for the volt meter connections.

E2 .025v closed, .025v open(ground)
IDL .029v closed, 4.75v open
VTA .536v closed, 3.5v open
VC 5.01v closed, 5.01v open

Look about right?

 

[jetjock]

Right hell, it looks about perfect. Assuming no flat spots in VTA at around 25% throttle (typical of worn sensors) you've got a fully functioning and properly installed TPS there.

VTA when closed is right at the midpoint of the 100 mv to 1 volt spec and although the TRSM states VTA open should be 4-5 volts 3.5 is typical. In fact I've never seen one beyond that. Bottom line: VTA falls between 100 mv and 4.8v throughout the range of throttle travel. Sorry, no code 41 for you.

VC is also fine. IDL is OK too although I was surprised it's 12v when high. I could have sworn it was pulled up to 5v like the other sensors but now that I check the book it should be battery voltage. The main thing is yours is showing a solid ground when closed and a good pull up to +12 when open. No code 51 for you either, at least not from that cause.

I'd say you're good to go. Cold and warm idle control should be active, as should idle up for AC compressor and headlight operation. Remember, if the TB is the older style with a manual bypass screw make sure it's fully closed.

One more thing. Technically you ought to be using E2 (sensor ground) and not battery negative when measuring sensors but since they're (sort of) connected together inside the ecu it's not a big deal. In the future try and reference E2. That way you'll avoid the .025 volts you saw between E2 and battery negative. It's nothing to lose sleep over though.

Nice job. Not like Mode $06 is it?

 

[cuel]

"Remember, if the TB is the older style with a manual bypass screw make sure it's fully closed. "

Hmmm..... That would be top center, correct? The cover is missing off mine, and I've always had a slightly high idle(around 850 warm). Gonna go check that.

 

[jetjock]

Right. Make sure it's fully seated.