jordanhere123

I have a 1994 pickup 4wd 22re with 151k miles . Earlier today on the highway the check engine light came on solid. I checked the codes and it appears to be showing code 21 and code 71. Truck seems to drive and run the same. I was thinking maybe the O2 sensor . I recently put a header on it and when the O2 sensor was out it looked old. Any help appreciated

chefdave

Hi
According to my haynes manual code 21 is oxygen sensor detrioration or open/short circuit in sensor heater signal. Code 71 is egr gas temp below pre-determined level during egr operation or open circuit egrgas temp signal. Both codes are listed as california only.
Hope this helps
Dave

scope103

I actually like the Haynes manual, but it doesn't hold a candle to the actual Factory Service Manual. And it's so much easier to get! http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

I actually have a California manual, and the only California-only code it lists is 27, open/short in the sub-heated O2 sensor (the down-stream sensor, which is California-only).

The most likely cause of a code 21 at this vintage is a broken wire right at the sensor connector, but the diagnostic is easy. http://personal.utulsa.edu/~nathan-b...01heatedox.pdf Of course, if the sensor is more than, oh, 5 years old it wouldn't hurt to replace it as well, even if the truck-side wire is the problem.

jordanhere123

I will check it with a meter. I only have one O2 sensor, before the cat.

jordanhere123

The O2 is reading low .03 or lower .

Would this be the correct O2 I need if I replace?

http://www.ebay.com/itm/234-4052-Toyota-4Runner-Pickup-2-4L-3-0L-Oxygen-Sensor-/310676015787?_trksid=p2054897.l4275#shpCntId

scope103

.03 ohms on the heater side of the sensor? (No handheld multimeter can read that low.) Or does that .03 refer to some other measurement?

For that kind of money, you can get a real Denso part from RockAuto. (I have no opinion, but many on this site are pretty sure Denso is the only manufacturer to use for O2 sensors.)

Personally, I don't like the semi-universal fit, where you end up with two connectors under the vehicle instead of OEM one. But if Denso likes it, who am I to argue?

jordanhere123

I reset the engine light 2 days ago and just came back on today. If the O2 sensor is the problem and I replace it, will the check engine light reset it's self or do I have to reset it ?

Terrys87

iTrader: (1)

I get my O2 sensors from www.sparkplugs.com Put in our VIN and get a Denso. Do not get the universal or Bosch if your sensor is in need of replacement.

Here is how I clean the EGR. You will most likely need to pull the Plenum and clean all of the hoses and pipes as they will probably be plugged as well.

I worked on the EGR. Here is another picture that may look like the wrong way to do this, but the screw will strip if you use a screwdriver. Get a good firm grip, but not so hard to distort the screw.


With the screw out, get another bite on the the pipe to get it out of the EGR. Leave the carbon in the pipe at this time as it will help keep the pipe round. The carbon is hard as concrete. Slowly work back and forth to get the pipe spinning inside the EGR tube and to start breaking it free. Could take up to 10 minutes but just be patient.


Here is me using a drill bit. I have never gotten as screw out with a Phillips screwdriver. Ususally rusted to bad. I use vise grips, then getting the pipe out is another job in itself. Take your time, you have to get this out to get all the carbon out.



After it is apart, I use a drill bit, screw driver, nail, clothes hanger to get all of the carbon out. It is rock solid in places. You can put vacuum on the hose and see and hear the plunger moving and operating inside the EGR, the goldish part.


If you take the Plenum off, Pull the Throttle Body off and take the Plenum to the carwash. The Thottle Postion Sensor is on the Throttle Body. Dont get it wet with water or cleaner. I just leave it on. You dont want the TPS giving problems. Where the EGR connects on to the Plenum, it will be very dirty. It has tubes that go through the Plenum so you wont be able to see all the way through. I take some kind of cleaner and spray into it to break up the carbon.


On the Brown Valve, just pop the black cap off and take an air hose and blow the paper filter clean.


All of the hose connections on the Plenum will more than likely be plugged to. Here to I use a drill bit with my fingers and get it all cleared out. Check the hoses also and make sure there is no carbon blocking them.


Here both the port and line is completely plugged with carbon. There were others plugged as well.

jordanhere123

Just received my denso O2 sensor from rock auto. Part number 234-4052. The sensor looks different from what was on the truck currently?

jordanhere123

This is my first time replacing the sensor since I got the truck. No idea when it was replaced last. The one in it now looks like a Bosch but has no markings? I just want to make sure I got the right one before I put it in so I know to send it back to keep it

Terrys87

iTrader: (1)

I am more familiar with the 84-88 trucks but the bottom sensor is what I see when using a Denso. You are correct the part number is usually 234-????

jordanhere123

Code 21 is taken care of, but code 71 has been coming on every 2-3 days. No clue what it is. Truck seems to run and drive fine again.

scope103

Seriously? You've been a member since May and never noticed one of the hundreds of postings to the manual?

Here you go: http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

Most likely, you have a blocked hose/tube somewhere in your EGR system. There are good, easy to use diagnostics in the manual. It may not affect performance, but you're poisoning everyone around you (including yourself).

Odin

Factory service manual is always a good reference but in a pinch you can look here http://www.4crawler.com/4x4/CheapTricks/TroubleCodes/

jennygirl

That looks like the right sensor, the denso ones look different but work better and plunge deeper into the pipe. I think headers can amplify the crappiness of the Bosch units. I had cruise CEL with a Bosch unit in my headers. The thing that fixed it for me was burping the coolant system..

You could also be running a bit lean, if you still get the CEL at cruise speed with the denso I would try two things..

- burp your coolant system (air bubbles affect ECT temp and cause messed up AFR and HOT exhaust temp)

If that doesn't fix it,
- try notching the AFM spring gear two to four clicks richer (counterclockwise)

EGR could also be getting too spicy and throwing the code due to overly hot exhaust temps

Good luck! Hope this helps

jordanhere123

Just an update. My egr valve was stuck closed but I was able to get it freed up. Seems to run better now. Didn't drive it much since I did that yet though.