Jasjavelin

Hello Yotatech,
This is my first post but I have learned alot from the forum in the last year after I bought a basketcase 89 4 Runner with 3vze/manual. After pulling the intake to replace the coolant line, I had code 52 and either 41 or 51 earlier this spring (cant remember for sure, pulled TPS and tested it/ordered new one). Successfully beat 52 with the info from yotatech, but CANNOT beat the 51 code. I replaced the TPS with a new one from Toyota and now have code 51 no matter what I do. Things I have done to beat this:

-new TPS installed/adjusted per 4crawlers website
-checked wiring between ecm and tps (checked out ok)
-checked voltage per fsm at ecm for each tps circuit (VC-E2 in spec, no voltage from IDL-E2 which is specific to the code 51 so this has to be the problem.
-according to FSM, IDL voltage for my model should be 8-14 volts with "throttle valve open"- NO matter what I do, I don't get any voltage at all.
-purchased ebay ecm to see if IDL circuit is busted on mine-same thing happened-even with just the ignition on, pushing the pedal starts a code 51. Letting off takes the code 51 away since IDL should be 0 volts with throttle valve closed. Rig also wants to die since it wont idle over 500 RPM and coming to a stop sometimes kills it.

I have looked/searched the site but cannot find how exactly the IDL circuit operates. Does the TPS send the voltage to the ECM via the IDL circuit grounding to the E2 circuit when the throttle is applied? If the TPS sends voltage this way, then I guess I installed the TPS wrong. I took the TPS off and with it attached to the ECM, I moved the little knob inside and never saw a spike of voltage. It ALWAYS registers O volts. From a diagram I found it looks like the IDL circuit grounds on throttle movement and sends a voltage signal back to the ecm. How come when I manually move it I dont see any volts? I am stumped and thought after beating 52 I could about do anything on these Toyotas, but 51 is worse it seems. I would appreciate anyone chiming in and telling me that the TPS is adjusted wrong as that can be fixed. Thanks for reading my struggles.

rustypigeon

E2 is the sensor ground. When throttle is closed there should be less than 2.3k ohms of resistance between IDL and E2 at the TPS sensor. The IDL circuit is therefore grounded when the throttle is closed.

When the throttle is open, there should be infinite resistance between IDL and E2. Because if this, you should show battery voltage when backprobing these terminal of the ECU with the throttle open.

The FSM has a flow chart for this condition. I am not sure if you already looked at this, but go to this link and go to page EG2-188 and see if helps...
http://personal.utulsa.edu/~nathan-b...86troubles.pdf

EDIT: before you do anything, make sure your TPS is adjusted according for factory specifications...
http://personal.utulsa.edu/~nathan-b...93throttle.pdf

Another quick check of this circuit is to unplug the TPS connector and put your multimeter on the terminal that has a yellow wire with white stripe (IDL) and the terminal that has a brown wire with a black stripe (E2). You should show battery voltage between these two terminals when the ignition is on.

Jasjavelin

Thanks for the good ideas. I went back through the TPS installation instructions and did them again. Took off throttle body, hooked up leads etc. This is what I got (and got before). Using my multimeter set to 20,000 ohms, my results:

VTA to E2, no clearance: 630 (spec is 200-800 ohms)
IDL to E2, 50 mm: 10 (spec is less than 2.3k ohms)
IDL to E2, 77 mm: open/infinite (spec is open/infinite)
VTA to E2, wide open throttle: 4.5 k (spec is 3.3k-10k)
VC to E2, all positions: 5.9k (spec is 4k to 9k)

So it appears to be within the factory specifications. When I set the IDL/E2 at 77mm, I set my multimeter to beep when open and I set it there. The reading was .010 on the screen at 20,000 ohms so I interpreted that (according to 4 crawlers Ohm page) to be 10 ohms. I may have messed that up, but feel somewhat confident about it.

I put it all back together and same thing at the ecu with the voltage.
IDL to E2, throttle valve open: .02 volts (spec is 8-14)
VC to E2, all positions: 4.87 (spec is 4 to 6)
VTA to E2, throttle valve closed: .08 (spec is .1 to 10)
VTA to E2, throttle valve WOT: .37 (spec is 3 to 5)

Ran through the troubleshooting page in the fsm link you provided. I checked the wires from the TPS to the ECM for resistance. All looked fine. Unless I have two bum computers, the only thing I can think of is maybe a ground got undone when I had the intake off fixing the knock sensor. I remember one on the pass side head at the rear, I cleaned it up and dielectric greased it. THere is one on the top of the intake, same thing, cleaned/greased. I checked the batt wire/ground to the ecm as well. Have full battery voltage to the computer. When I put my leads in the IDL pin and the E2 pin on the ECM, the code goes away, but when I rev up the motor, it cuts out at 2000 rpm.

RJR

Check to make sure none of the wires in the harness between the TPS connector and the ECM are shorted to ground. If you just checked for continuity of the wires, you could have missed a ground short.

Jasjavelin

Just got back from running a new wire for the IDL and VTA circuits. Didn't run a new ground (looks like it is tied into several different places before going to ecm and didn't want to disturb them) or a new VC wire since it seems to be working correctly. Same voltage as before on IDL and VTA circuits. Is the TPS that particular that even setting according to FSM, it may still be off?

RJR

These measurements look good. Nothing wrong with the TPS or the adjustement.

The IDL to E2 measurement with open throttle is bad, and so is the VTA to E2 measurement at WOT. To troubleshoot further, try the following:

Disconnect IDL from the ECU at the ECU, set the throttle to WOT, and measure the voltage on the ECU pin (ignition on). It should go to 8-13 volts. At the same time, measure the resistance from the disconnected IDL wire to ground. It should be open (infinite.)

Now, with the ignition still on and the throttle set to WOT, disconnect the VTA wire from the ECU and measure the voltage on the disconnected wire. It should be close to 5 volts. Now measure the resistance looking into the ECU pin. It should be fairly high (>10K).

Hopefully one or more of those four measurements will fail the limits I've given, and that will narrow down where the problem is.

Jasjavelin

RJR, I think we are getting closer with your idea. I disconnected the IDL wire from the ecu, throttle open or closed, there was no voltage from either the tps or the ecm. Resistance was factory spec.

We might have something with the VTA/E2 circuit. I happened to check resistance with both the E2 wire connected to the ground at the ecm and without. With the E2 wire my VTA specifications were WAY off. factory spec for that circuit is 3.3k-10k, mine all hooked up was 1500k. Thought that was strange since the TPS was all in spec the last time I set it. Thing is, I set the TPS off the engine, not hooked into the wiring harness. I disconnected the E2 wire at the ecm, and lo and behold, resistance was back in spec, but ONLY if the ground was disconnected before the ecm.

VTA Voltage, With it disconnected from the ecm, it had .08 volts throttle closed/ .37 volts throttle open,(like before). By disconnecting the E2 wire from the ecm, voltage changed a little on the VTA wire from the TPS. voltage bumped up to .11 throttle open, .38 throttle open.

I checked the resitance on the VC circuit too with E2 connected to the ecm, and it was off like the VTA circuit until I unhooked the E2 wire and went back to spec. voltage was factory spec, like before at 4.6 volts

I checked the IDL-E2 voltage at the TPS with the E2 ground disconnected at the ecm, and voltage increased from the .02 I got before to .10 on the IDL wire.

SO, what does all this mean? I have no idea. Apparently, by adjusting the TPS off the vehicle screwed up the resistance values on the TPS when I put back on. By disconnecting the E2 ground wire at the ECM, all the resitance values went back to spec. It also increased the VTA and the IDL voltages, but not to where they need to be. I think we may be on the right track though. I also did all this with my extra ecm, same results.

RJR

The IDL terminal should be pulled up internally by the ECU, and pulled to ground when the IDL switch in the TPS closes. The fact that the ECU is not pulling that pin up on two separate ECU's suggests that that part of the ECU is not getting power. I have no definite knowledge as to how the power is distributed inside the ECU, but I would check to see if there is +12V on pins 12 and 13 of connector A of the ECU. Those appear to be the closest power pins to the TPS section of the ECU.

rustypigeon

The connector is supposed to be disconnected from the TPS when checking the resistance values of the TPS. When you leave a connection to the ECM, you are factoring in resistance inside the ECM itself. NEVER check resistance of a computer circuit unless directed to by a FSM. When you are checking for resistance, the multimeter is outputting voltage. You don't want that voltage from your multimeter going somewhere that it is not supposed to be.

Checking voltage at the ECM with a high impedance multimeter is safe. Checking resistance at the ECM may cause problems.