FIXED: Pulled MAF codes today from ECM... Code 157 158

[doonze]

So last two days I've been having a cutting out issue, I have another thread about that, but I pulled these codes just now....

157
(R,M)
Mass Air Flow signal is/was low or grounded - MAF

158
(O,R,M)
MAF sensor is/was high or short to power - MAF

So I'm thinking this is why it's been cutting out..... so do I just need to clean it or what would/could these codes mean?? Thanks!

 

[MrShorty]

Sometimes "exactly" what a code means depends on which part of the test it came from. If I assume you didn't run the KOER test, then the first question I would ask is if the 158 is a KOEO code (1st set output during the KOEO test) or a CM code (2nd set output during the KOEO test), or both.

A KOEO code means that, when the PCM tested the KOEO "baseline" signal for the given sensor, it was out of range, which almost always means some kind of electrical fault (either in the sensor or in the wiring to the sensor).

A CM code is set during normal operation and means that, at some point, the PCM couldn't reconcile data from the sensor and other engine operating parameters.

SOP when diagnosing codes is to resolve KOEO codes first, then KOER codes, then CM codes.

If you aren't certain how to distinguish between KOEO and CM codes, I would suggest reviewing my "notes on pulling EEC-IV codes" thread in the EEC-IV forum.

 

[doonze]

Just the person I wanted to see posting a reply!! Ok, sorry for the lack of better info, It was a CM code, my KOEO is 111, then I got my 157, 158, and my normal 176 O2 code. I didn't bother with a KOER test run, it hasn't been throwing the code unless moving so I didn't think I would get anywhere with that.

I've also noticed a slight decrease in power since the cutting out thing started. I cleared the codes and I will see if it throws them again tomorrow or if it cuts out. I did take the MAF out and cleaned the snot out of it. The codes haven't been thrown when it cuts out, but the CEL had been coming on much more often today. I comes on every once in awhile with the 176 code, and has since I got it, sometimes it will go days without that code. But the last day or so it's been going off and on, sometimes even just after starting it. I think it's these new codes setting it off so much. Will post more info tomorrow.

 

[MrShorty]

I would run the KOER test, just to see if it can see the faults or not. If it passes the KOER test, that indicates that the faults are more intermittent, which will make them more difficult to track down. If codes do show up, it is often easier to diagnose from the KOER test (because the fault is occurring during the test).

The codes suggest something wrong with fuel mixture. At this point, it is hard to say if it is something in the MAF, something in the O2 sensor, or a vacuum leak or fuel delivery issue that is throwing off the mixture. I haven't looked up the diagnotic trees in the books, but I'd probably start by:
1) run the KOER test.
2) check for vacuum leaks.
3) check fuel pressure.
4) check wiring to MAF and O2 sensor to make sure there are no loose connections.

 

[doonze]

Ok, I had cleared the Codes and Yesterday pulled the codes again. Here's what I got.

KOEO
111
CM
157
158
176

KOER
998
157

Cleaning the MAF did nothing to help the issue. Now the CEL light is on more then it's off, Seems to be the two MAF codes throwing the light. Runs WORSE when the CEL is off then when it's on it seems. Still cutting out.

I would think for the MAF to be showing out of bounds too low and two high would almost have to be a MAF issue. If I had a fuel problem, but was still able to have air flow, I would think it wouldn't cause the MAF to go out of range. Unless it's tied to the O2 sensors, and it's just saying the air flow is too high/low for the amount of fuel being burned. But the only other code I'm getting is the 176, and I've had that since I got the truck. I've checked the connections on the MAF, I'll check the O2's in the next couple of days or this weekend. I would think if it was a fuel delevery problem, and making the engine run lean, it would throw a code for both 02 sensors, not just the one... Just don't have the cash right now to drop $130 on a new MAF so I guess I'll run everything else down first. Going to track all the MAF wires to make sure they haven't gotten into the belt or anything. Maybe finally break down and get a Multi-meter again since my last one died. See what my voltage is.

 

[MrShorty]

I've seen this scenario come up a few other times on this forum. I don't recall any good, specific diagnostic advice, but it seems taht every time this scenario turns out to be a bad MAF. I would agree with your plan to make sure it isn't a wiring fault somewhere, but "diagnosis-by-gut-feel" is that this one is going to turn out to be an MAF.

 

[doonze]

I've seen this scenario come up a few other times on this forum. I don't recall any good, specific diagnostic advice, but it seems taht every time this scenario turns out to be a bad MAF. I would agree with your plan to make sure it isn't a wiring fault somewhere, but "diagnosis-by-gut-feel" is that this one is going to turn out to be an MAF.

My gut agrees, I did search for answers before I asked here and the general idea seemed to be the MAF was faulty, but some people never posted their resolution, and for others it took many MAF's or they keep frying MAF's, so I was looking for any ideas.

I did disconnect my MAF today and ran without it to see how it did. It ran like an old, wet, blind dog. The throttle was less then responsive, I would have to get into the gas much more then normal to get a response. My thinking is the MAF must be tied to the timing somehow, and it's not getting advanced like it should when it's out of bounds and the computer is ignoring it. From back in the old carb/distributor days this is what I would compair it too, vacuum advance not working correctly. Course give me a quadra-Jet and a HEI distributor and I'm in my zone. I'm still learning all this computer crap.

So anyway, once I disconnected the MAF it didn't cut out once. Could just be coincidence, but I'm keeping the MAF DC'd for now so I'll know for sure by tomorrow night. But both the CEL's and the cutting out seem to be due to MAF malfunction.

My thinking is if the MAF is tied somehow to the timing, the CPU is getting the complete opposite signal from what it should in certain situations, and it's causing it to cut out. At least that's the thinking for the moment.

Any bad nasty things going to happen for disconnecting the MAF I need to know about? I mean my wheels are not going to fall off, or my pistons aren't going to disappear into a dimensional rift or anything right?

 

[fixxxer]

With the MAF disconnected, the ECM should use the "limp-home" programming, less than stellar performance from the engine but the engine won't burst into flames either. I'd like to see if it throws any different codes with the MAF unplugged, other than what would be expected, to see if there's a short somewhere, the ECM would see some kind of feedback signal telling you it's getting all or part of it's MAF signal from a shorted wire.

 

[doonze]

Well, it's for sure throwing a code, CEL is nice and amber from key on to key off now. The CPU is defently pissed about the missing MAF. I'm gonna pull the codes again tonight when I get home just to see what it has to say.

And other then being a total dog, the truck runs as perfect as I could ask with the MAF disconnected. "limp-home" works better then "regular" mode it seems, maybe my MAF has been going for awhile, just finally bought the farm and threw lights, and started my cutting out problem. The cutting out seems 100% solved, I've made the 15 mile trip home and the 15 mile trip back to work now and hasn't cut out once, was doing it 2-4 times in a trip that long (each way), so I'm more at piece in my own mind at least. It's not going to leave me on the side of the road just yet! I will post up codes and give a fixed update once I've managed to track down a new MAF. Anyone want to loan me $180 for a new MAF?? Or how about just $130 for a rebuilt MAF?? LOL

 

[boggs1227]

my 2 cents .......


have you checked the wire harness connector that goes to the maf ?

( as with anything on these truck is that plastics and wire insulation wear out and become bad over the years...had a dpfe unit that had a bad wire harness end )

have you been unpluging and reconnecting the maf alot ?? problem i had with mine maf gong out was that the small rubber boot that is inside the connector houseing can sometime move around on you .i to had my maf throw a cel at me till i found out the boot had become dis-logged and was makeing the connector's keeper tabs ( on the side of the connector ) not hold onto the maf sensor but yet it looked ok to the eye.

 

[Alan_V]

Well, it's for sure throwing a code, CEL is nice and amber from key on to key off now. The CPU is defently pissed about the missing MAF. I'm gonna pull the codes again tonight when I get home just to see what it has to say.

And other then being a total dog, the truck runs as perfect as I could ask with the MAF disconnected. "limp-home" works better then "regular" mode it seems, maybe my MAF has been going for awhile, just finally bought the farm and threw lights, and started my cutting out problem. The cutting out seems 100% solved, I've made the 15 mile trip home and the 15 mile trip back to work now and hasn't cut out once, was doing it 2-4 times in a trip that long (each way), so I'm more at piece in my own mind at least. It's not going to leave me on the side of the road just yet! I will post up codes and give a fixed update once I've managed to track down a new MAF. Anyone want to loan me $180 for a new MAF?? Or how about just $130 for a rebuilt MAF?? LOL

I replaced mine a bit over a year ago. Got it from Pep Boys currently $90 online. I compared the stampings on the part and I believe it was an OE part.

Just checked and Auto Zone is the same price, but you have to pay $60 refundable core charge.

 

[doonze]

I replaced mine a bit over a year ago. Got it from Pep Boys currently $90 online. I compared the stampings on the part and I believe it was an OE part.

Just checked and Auto Zone is the same price, but you have to pay $60 refundable core charge.

AZ only shows me 2, Reman for $127 and new for like $178, O'Reilly's Shows me a Reman for $79.00, so I'll prob grab that one, 1 year waranty, I think if it makes it the first year it'll be ok.

 

[doonze]

Ok, finally got a "new" MAF today. Cleaned it up and seems to be working fine, no cutting out like it was doing before I disconnected the old MAF, I'm still getting a CEL, but I was getting my 176 code since I bought the truck and it seems to be that code that is throwing the light. I will pull the code here in a few hours and make sure. But I just wanted to update FIXED on MAF codes, by replacing with a U-pull-it MAF from another Explorer. $32 with tax. .

 

[doonze]

Hey, can a mod please change my original title to "Fixed: PCM MAF codes 157, 158" please? Thanks!

 

[solumized]

Hey guys.

I'm experiencing the same codes thrown as you were doonze. 158 and 157. I tried cleaning the MAF with the cleaner I bought and it gave me hope thinking all i needed was a new sensor because the CEL would start to go on and off intermittently instead of constantly on. I just picked up the new MAF today and installed it and it's still throwing me the 157 158 codes. My two questions are is there anything else I should do to try and fix this and also are there any wiring diagrams I can go through to check the wiring to see if it's not just a bad connection somewhere. I'm going to clear the codes tomorrow and see if that fixes it. If it doesn't going to try the battery disconnect and reconnect to see if that works. When my CEL light comes on my RPM's jump up around 500 from 1500 to around 2000 at 55 mph. When the light goes off it goes back down to 1500. The truck is also sluggish to respond to gas when taking off from stop but once above 1500 rpm it takes off just fine. Any help would be greatly appreciated. I need my truck to last as long as possible. Can't afford a new one right now. It's a 93 with 210k miles.

 

[doonze]

Hey,
Well, I wish I had more info for you, the codes maybe the same but the symptoms are different. When mine first started the truck just "cut out" every so often, like I had turned the key off for a 1/2 second, then all would be fine again. I unplugged the MAF alltogether and that fixed the "cut out" issue, but my CEL was lit 100% of the time (because maf was missing), and it was a bit of a dog, no power, etc.

But my "new" used MAF did fix my issues. I am sorta getting a 157 again, but I think it's related to a iffy O2. It won't throw the CEL but once every few months, and then just for a singe drive, then it won't come back again. The truck run no different when the CEL come on then when it's off.

As far as troubleshooting, there are lots of threads on here about troubleshooting a MAF. Also I've heard chiltons has TS info as well.

 

[fullmetal6]

I got these codes as CM after stalling in 2 feet of water. I cleaned the MAF and tested it. It appears to test ok. I reset the code by pulling the jumper with key on engine off. And 157 popped right back on. Any other ideas?

 

[Kevinh71047]

I was wondering could you tell me where my maf wires go to on the truck i think the red wire from the maf goes to the battery the reason i was wondering so i can check those wires out with a meter

 

[shaverdc1]

Well, it's for sure throwing a code, CEL is nice and amber from key on to key off now. The CPU is defently pissed about the missing MAF. I'm gonna pull the codes again tonight when I get home just to see what it has to say.

And other then being a total dog, the truck runs as perfect as I could ask with the MAF disconnected. "limp-home" works better then "regular" mode it seems, maybe my MAF has been going for awhile, just finally bought the farm and threw lights, and started my cutting out problem. The cutting out seems 100% solved, I've made the 15 mile trip home and the 15 mile trip back to work now and hasn't cut out once, was doing it 2-4 times in a trip that long (each way), so I'm more at piece in my own mind at least. It's not going to leave me on the side of the road just yet! I will post up codes and give a fixed update once I've managed to track down a new MAF. Anyone want to loan me $180 for a new MAF?? Or how about just $130 for a rebuilt MAF?? LOL

go to rockauto.com they r alot cheaper there