Jipopotamo

Ok: 87 4runner 4x4 EFI 22RE 5spd

Brand new Denco O2 sensor, new 16 ga shielded wire from sensor to computer, new remflex gaskets throughout and reset the computer.
But I am still getting a code 21. So where is the break down?

thook

How is the vehicle running otherwise?

Jipopotamo

Mileage seems to be lower than it should be.
Rough rough cold idle. Hot idle is pretty smooth.
Every now and then I get a climbing idle speed that results in the surge cycle (comp kills gas, vehicle tries to stall, gas restored, nice normal idle speed, starts climbing up again.)
This cycle can be broken if when the idle starts climbing, I tap the gas pedal. This seems to "break the cycle" and the vehicle goes back to idling normally, or sometimes will restart the climb cycle.
WOT feels restricted and restrained. My max available power seems to be somewhere in the 1%-35% of initial throttle. Everything after that seems to change nothing noticeable.
Makes heads or tails outta any of this?

DeathCougar

iTrader: (23)

have you tested the TPS per the FSM?

vital22re

iTrader: (2)

clean the throttle body and test/reset the tps.

thook

I'm pretty darn sure code 21 on your year is the equivalent of a code 5 on my '86. Which would mean there's fault detected along the circuit. IOW, at the point the ECU sees conditions as being correct to go into closed loop (engine's at operating temp and ECU utilizes O2 voltage feedback to know what's going on with a/f ratio and then starts it's a/f ratio modifying for catalyst efficiency.....whew), The code indicates that the ECU is unable to make corrections to the a/f ratio based on the input the O2 is giving it. Last time I had a code 5, I finally figured out I had a bad AFM. Though, I didn't get the idle bounce and fuel cut.

Read this:
https://www.yotatech.com/forums/f116...ng-bad-215640/
If it doesn't make sense, I'll try to explain. Needless to say, go ahead and test the TPS, clean the throttle body......as suggested, but the TPS may not be the problem.

sb5walker

The ecu will generate a code 21 either if there is a fault in the circuit, OR, if the sensor isn't "switching" fast enough. Normally the ecu adjusts mixture to where the sensor will switch from slightly rich (higher volt) to slightly lean (lower volt) at least once a second. If the sensor is fouled or bad for some reason, or there is a problem with the wiring or with the mounting position, the switching rate can be too slow ("lazy" sensor) and the computer will throw a code.

Since the 87 uses a one-wire sensor, it grounds through the exhaust, so check resistance between the body of the sensor and the neg batt post. If more than a few ohms, pinch a ground wire under one of the sensor mount bolts and lead to a good ground. Reset the computer, & see if it comes back.

If the ground is okay, then check the switching rate. I think 87 is the first year of the new type computer with more codes, yet it uses the old one-wire O2 sensor type. From 88 on they used a four wire sensor with a heater circuit. So 87 is kind of a hybrid/transition year and to be sure of the testing procedure it would be good to have the 87 manual.

But if you don't got, and your check connector looks like the later trucks, then you can probably use the 93 instructions for testing switching, which involves grounding TE1 to E1 and then looking for voltage changes on VF1: http://personal.utulsa.edu/~nathan-b...42oxygense.pdf

If the check connector is the older type, then the procedure on page FI-70 in the 85 manual might be the right one: http://groups.google.com/group/alt.a...lnk=raot&pli=1 I think the OX sensor check connector has green and black wires, and you're looking for at least 8 changes in voltage in a 10 second span. Also, you should have at least 3.75V with motor hot and running.

thook

But, you know what, man? I went through all those checks on my sensor and it was still a problem with the AFM. I had dropouts along the Vs track. Replaced the meter and the CEL went away. Took me a long time to figure out what the problem was.

What would you say in this circumstance? Since the '86 models use only code 5, was it that the voltage signal was staying to one side of the volt swing too long? IOW, indicating a rich/lean mixture, but due to the OBD design limitation, all I got was code 5? Couldn't get much of straight answer from anyone I'd talked to at the time, so made my best "educated" assessment.

Team420

Check your part #'s..... I found out the hard way that o2's for a runner, are not the same as o2's for a p/u, I had the exact opposite problem... I got a new o2 for my 91 p/u, and it was actually an o2 for a runner....

Jipopotamo

Tons of solid information guys, awesome stuff. I have the day off today so I'll get to testing and let you know what I find. The vehicle has over 240,000 miles on it and I know the AFM and TPS are still original so I am biased to expecting issues from them. The hunt begins.

Jipopotamo

TPS REPORT #1

Ok so I had the chance today to get the multimeter out and start testing. This was a test of the throttle position sensor on my 87 4Runner 22RE efi. The methods and criteria for testing was via 4Crawler. Here ya go.

Test || Terminals || Resistance || Acceptable Range
1 || VTA-E2 || 664 || 200-800
2 || IDL-E2 || Open/Infinite || <2.3K
3 || IDL-E2 || Open/Infinite || Open/Infinite
4 || VTA-E2 || 4.37K || 3.3K-10K
5 || Vcc-E2 || 6.20K || 3.0K-7K

Link to testing methods and terminology:
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

My TB was off the vehicle and the TPS was tested while on the TB and while off.
All tests were within specifications expect Test #2 between the IDL-E2 pins at .57mm.
The distance was simulated as were other distances in an attempt to create a reading from the pins that were not the beginning control reading of 45 ohms and the instantly achieved open/infinite reading produced as soon as you rotated the TPS shaft.

I can't produce a reading from the IDL-E2 circuit that is not the beginning reading of 45 ohms or the open/infinite reading. Is this enough of an information failure to require replacing the TPS? I am soaking the TB now and will clean it out and I have special solution to clean the TPS itself with. Or do I need a new TPS altogether with those test results? Thanks for the help.

Jipopotamo

AFM Report Via 4Crawler methods and terminology

Static Test 1-5 were within range and acceptable.
Dynamic Test 1 part A and B were solid pass.
Dynamic Test 2 part A was within range and acceptable.
Dynamic Test 2 part B (E2-Vs; range stated as 20-1000. I had fluxing rates much higher than 1000. A wide range from 1000 up to the 2.2K area.) According to specs, this isn't a pass. Is this a replaceable fault or a simple clean up or no issue at all? Thanks much.

Link to 4Crawlers write up:
http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

neon_jaguar

I feel your pain, I ran through a lot of testing voltages here and there, even testing the cable from the ECU to the O2 sensor, for the life of me i could not get rid of code 21.
I read somewhere that you should disconnect your neg. terminal and remove your ECU.
Then pop off the top and look at the circuit-board itself, there on the bottom left (assuming pins face you) there will be a fried gray resistor.
Run down to your local radio shack, get a new one (somewhere around $0.90) solder the new one in, and your good to go.

masmith73

Same problem here. I have a '93 pickup, 22RE 2x4 CA emissions, and after years of frustration getting it past smog I decided to do something about the CEL that just wouldn't die last weekend. Ran the diagnostics for the O2 sensors and they were operating as they should but still had the code 21. After reading this post I decided to pull the ECU and have a look:



So here's my question: Does anyone know the rating of my blown resistor? The other two resistors appear to be 0.43 and 0.15 ohms (I believe the 'K' indicates the rating tolerance); and since they are both different ratings It's kind of a crapshoot as to what the blown resistor's real rating is.

Thanks!

CaratFive

How relevant. I just put in a new O2 Sensor and am getting a code 21. Lo and behold this old thread was bumped. Checking for fried resistor tomorrow. What incredible timing, however. I put in about 400 miles on the new sensor and it just now started throwing a 21. Gas mileage went from 11 to 17ish though. fantastic.

abecedarian

I don't know the rating but have you tried just heating and re-soldering the leads?

TNRabbit

FYI: NEVER soak a TPS. You'll destroy the inner circuits.

masmith73

Nope, but it's probably worth a try. The board looks pretty brown around it and the resistor itself looks like a toasted marshmallow, so I just figured that it's blown. I picked up a used ECU on ebay yesterday which I'll probably just put in instead. Just for the fun of it though I think I'll try and repair the board once I get the replacement and post the results.

scope103

1. I don't know the resistance of your resistor
2. I can't see much from your photo, but just because a resistor looks "toasted" does NOT mean it is toast. These are power resistors; they are supposed to be very warm. What do you get when you put an ohmmeter on it?
3. I really doubt you have a "0.43" or a "0.15" ohm resistor. (And you won't be able to measure that with any ordinary ohmmeter). You might have a 0.43K (430ohm) resistor, but I've never seen one marked that way. But: see #1.

masmith73

Man I love this site. @scope: exactly the kind of direction I needed given that I know very little about electronics. Here's a pic of the new module:



Plugged it in and it worked like a champ. I spent years dealing with this problem and it only took an $80 used part and a few minutes to fix it!

So scope, if I take the good module to Fry's do you think they could match the resistor?