Questions on Codes and computers 92 explorer sport 5spd

[merc2dogs]

Hello,
I had the cel coming for a few minutes, then shut off, not flashing, on for a few minutes, then off for anywhere from a few minutes to an hour, stopped at advance auto on the way home, and had them pull codes for me
ended up with two seperate sets of codes:

111 system checks ok

Since the only definition I've ever found for this code IS "system checks ok", a question, does this mean the whole vehicle checks out good, or does it mean the obd system is working right?

also popped up with a 522, which was expected because I bypassed the switch, so nothing there.

as this didn't show anything I started home to dig in with a voltmeter to see if I could find any faults, on the way home the CEL came back on again as I was passing the next advance (yeah two close together, one at 68th, and one at 44th) so I pulled in and had them pull codes:

522 again

157 Mass Air Flow signal is/was low or grounded

171 Oxygen sensor not switching - system was at adaptive limits - Single, Right or Rear HO2S

173 Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S

179 Fuel system was rich at part throttle Single, Right or Rear HO2S

once I'd gotten home I went through and checked out the engine and underhood wiring, and what I found was that the crank vent hose (from the intake tube to the oilfill) was off. apparently fallen off somewhere as it was gone, and the intake hose (tb to maf) was loose. put on a vent tube from the old engine, tightened up the intake hose and checked all the electrical connectors on the truck to make sure everything was tight. then had to make a 20 mile run, and the CEL never came on, which brings up the next question, would that vent tube, and the hose being loose effect the rest of the system and cause the codes and CEL?

In other words: How interdependant are the MAF, TPS and O2? I mean, if I have my foot down to go 50mph, and the TPS sees the same position as 50mph, but the MAF only sees airflow for say 35mph,will it kick in a richer fuel mix thinking I'm struggling up a steep grade making the O2 try to lean out the mix??

also the bypass I did on the clutch switch, would that effect anything? there has to be some reason for the computer to obtain that info,I figure if it reads clutch pedal position, it must use that info somewhere. It does keep the cruise control from working, it was bypassed because the clip was off when I bought the truck and the previous owner had a string and some other crap tied around it to keep it in place that was underfoot when I took the test drive, so when I bought it I bypassed it for the drive home and never saw reason to change it.

one more thing, second code reader gave the codes, but didn't print out the definitions as they normally do, just gave a 'no definition available", the operator, a normally competant guy I've worked with a lot, claimed that it was my on board computer that was supposed to be providing the definition, and since it wasn't, it (my computer) was faulty and needed to be replaced, to my knowledge, the trucks computer DOES NOT provide the definitions, just the code, and it's up to the reader to provide the definition (or up to the operator to translate them) am I wrong on that?

and, in case the guy was right about the computer being faulty, how well would a 91 EB explorers automatic computer work on the 92 with a stick? I know on the older rangers/B2's you could use the auto computer with a stick, but the sticks wouldn't work as well with an auto. simply because the trans controls weren't there.

ken

 

[MrShorty]

So many different questions. Hopefully this will be organized enough.

1) "111 system checks ok Since the only definition I've ever found for this code IS "system checks ok", a question, does this mean the whole vehicle checks out good, or does it mean the obd system is working right?" 111 is indeed the "pass" code. I hate to call it a "system" pass, because there are three sets of codes, and you could pass one set and have trouble codes in the other two. 111 in all three sets of codes (KOEO, KOER, and memory) means that everything the EEC-IV/OBD computer monitors looks/has looked normal to the computer. There are a lot of things outside of the EEC-IV system that the computer doesn't directly monitor (fuel pressure, for example).

2) "would that vent tube, and the hose being loose effect the rest of the system and cause the codes and CEL? In other words: How interdependant are the MAF, TPS and O2? I mean, if I have my foot down to go 50mph, and the TPS sees the same position as 50mph, but the MAF only sees airflow for say 35mph,will it kick in a richer fuel mix thinking I'm struggling up a steep grade making the O2 try to lean out the mix??" That sounds like a good description of how a missing hose (or other vacuum/air intake leak would trigger any/all of those codes. The computer monitors/uses multiple sensors to set fuel mixture, including the MAF, TPS, and O2 sensor. When it sees inconsistencies in those sensors (like you describe), it can trigger trouble codes. The computer doesn't know why the inputs from the various sensors are inconsistent, but it can't reconcile the data it receives, and so it sets a trouble and turns the light in the hopes that you can figure out (and repair) the problem.

3) "also the bypass I did on the clutch switch, would that effect anything? there has to be some reason for the computer to obtain that info,I figure if it reads clutch pedal position, it must use that info somewhere. It does keep the cruise control from working, it was bypassed because the clip was off when I bought the truck and the previous owner had a string and some other crap tied around it to keep it in place that was underfoot when I took the test drive, so when I bought it I bypassed it for the drive home and never saw reason to change it." -- The computer uses the PNP switch to anticipate engine load. Basically, if the transmission is in P/N, even if the engine revs up, there's no load on the engine, so the computer can use a slightly different strategy than when it's in gear and the engine will actually be working. I doubt it has a very big effect on performance, but that's what I believe is going on.

4) "one more thing, second code reader gave the codes, but didn't print out the definitions as they normally do, just gave a 'no definition available", the operator, a normally competant guy I've worked with a lot, claimed that it was my on board computer that was supposed to be providing the definition, and since it wasn't, it (my computer) was faulty and needed to be replaced, to my knowledge, the trucks computer DOES NOT provide the definitions, just the code, and it's up to the reader to provide the definition (or up to the operator to translate them) am I wrong on that?" -- I'll preface my comment by saying, I've never used a scanner/code reader to get codes. I've always used a jumper wire and either a voltmeter or the check engine light as described under tests at www.dalidesign.com/hbook/eectest.html (you should try it sometime so you're not dependent on Advance or anyone else to get codes for you next time). I would agree with you. From everything I know about the EEC-IV self-tests, the code output consists of a series of organized voltage pulses. There isn't, as far as I can tell, any means for the EEC-IV computer to send any other form of data (such as a code definition) to the scanner as part of the self-test.

How's that? Make sense?

 

[Glacier991]

My understanding is that in either OBD-1 or 2 the vehicle only outputs codes. It is up to the scan tool to provide codes, either in booklet form, or in nicer ones, electronically by lookup table built in - and displaying them on the screen.

 

[merc2dogs]

Cool, thanks guys, was pretty sure that all the computer gave was codes, not definitions.
The vacuum leak must have been the source of the trouble because as yet the cel hasn't come on.

Plan to wire a switch into the clutch wires, I'd like to be able to use my cruise control once in a while.

I guess the confusion on the 111 code was because I'd see it along with a few other codes

Oh, I do know how to read the codes, it's just that I'd been driving for a few hours with it coming on an figured I'd take a break while I had it checked.

Thanks again.
ken.