I have a 94 bronco with the 5.0. Got some engine codes from doing the self test and this is what I got

334 and 637

How do I fix these considering I've never heard of the DPFE or EVP or TOT sensors.

It's been awhile since I've been on guys n gals. Just bought this bronco and never ever heard of these codes. Thanks in advance!

 

334 is a EGR code and 637 shows trans fluid temp sensor out of range. I would clear the code and see if they return.

 

Thanks southern! I'll try it out. My check engine light comes on after the truck is up to temp usually. But I have no cats

 

Your Bronco does not have a PFE (Pressure Feedback EGR) sensor. Instead, Code 334 indicates the EVP sensor was reading higher than expected which usually means one of two things. Either the sensor itself has failed or the EGR valve is not fully closing. Cleaning the EGR valve is the first recommendation since it rarely costs as much as a new EVP sensor. A pipe cleaner through the small holes in the bottom of the casting is the best method. Just take care not to puncture the bottom of the vacuum diaphragm above. The pintle needs to fully seat into the bottom of the valve when it closes. The EVP (EGR Valve Position) sensor is mounted to the top of the EGR valve with three small screws and has a three-wire connector that connects it to the main engine wiring harness.

Code 637 indicates the transmission fluid has overheated at some point OR the TOT (Transmission Oil Temperature) sensor has failed.

 

Grey streak thank you! I'm gonna clean the EGR tomorrow then. I'm guessing that the fluid must have overheated before I got it. Trans shifts perfect and has a nice red tint to the fluid

 

With the 600-series Codes, its best to clear them once and see if they come back before assuming the problem still exists. If you don't have any shift issues and the fluid looks good, let it go for now but pull Codes periodically to see if the same Code comes back.

 

Alright so yesterday I Reset the computer(I believe, I just unhooked the battery for around 15 minutes) and I drove the truck a good 30 miles. Check engine tool awhile to come back but it did here's the codes:

KOEO:
637
334

CM:
17
23
34
637

I checked out the EGR and it looks brand new. So I'm wondering if that EVP sensor did go out. Also the same with the TOT sensor. The codes 17 and 23 make no sense because I think they are KOER codes, correct me if I'm wrong. 34 has to do with the EGR. I did the self test about 80 times this morning after driving the truck and getting it to temp so I'm sure I read them right. What y'all think? I'm no good at this OBD-1 thing. Been awhile since I've had an OBD-1 bronco. Thanks!

 

You either get two-digit Codes OR three-digit Codes. Not both. There is a two-second pause between each digit of the Codes and a four-second pause between Codes.

This leaves you with CM Codes of 172, 334, and 637.

Code 172 indicates a lean O2 sensor reading or a non-switching sensor. The test for this requires an unlit propane torch and some throttle maneuvers.

Code 334 (See my original response).

Code 637 (ditto).

 

Oh ok, I'm guessing I know why it's running lean, probably cause I have no cats and no rear o2 sensor

 

There is only one O2 sensor on the EEC-IV-equipped trucks. It is at the junction of the arms of the Y-pipe in the exhaust. If there is no O2 sensor in the truck you will be chasing issues forever.

 

There is an o2 sensor in the y pipe, I just thought there was 2 lol. So would replacing it fix that? I do have a couple exhaust leaks at the flange on the manifold

 

Fix the exhaust leaks first, then loook for vacuum leaks. Your sensor on top of the EGR is probably faulty too.

 

Replace the O2 sensor FIRST and check the wiring to it while you are at it. One bad sensor in the system will have a "domino effect" on the rest of it.

 

Since you have removed Catz and still the O2 sensor, it may be sleeved up like a spark plug thread, or not. The O2 would be somewhat useless, throwing an EGR code if Sensor atop the EGR isn't faulty. The Map would try to inject more fuel, as the open loup system is faulty. The best fix for your situation is an exhaust shop, install the catz and proper O2 system.

 

It has the stock y pipe still, with the o2 sensor in the regular spot. Looks like the factory one from 94! I'm fixing the manifolds with new ones and new studs(I don't think there is a donut gasket correct?) and replace the o2 sensor, thanks guys!