Do I need a new PCM?

[tstripe76]

2013 Expy (220K miles) with a crank but no start condition. Getting codes P1636 and P2107 (also a couple for the O2 sensors but dont seem to be related). Was driving down the road, and it suddenly just shut off, like someone killed the power. No stumbling or strange noises (like a timing chain or something). Has a brand new fuel pump. So far have tested and have fuel up to the fuel rail, have spark at the plugs, and the crankshaft position sensor seems fine, as i get a reading of 150 rpms on my scanner when turning it over. I have not checked for compression but figured based on circumstances that is not the issue. I have tried to "reset" by leaving battery disconnected for a couple of hours. I have visually inspected the wire haresses that come off the PCM under the hood, and nothing jumps out, but everything is still in the protective sleeves, and dont see any signs of damage or cause for concern when checking that. Worth noting that if i let it sit for a few hours, and try to start, it will usually start for about 0.75 seconds, just enough for you to think yeee.. oh. I have searched quite a bit online, and most posts i see with both of these codes indicate needing a new PCM, or testing out any of the items already mentioned above. I have NOT taken the front of the engine apart to check the timing chains, and not afraid to, but based on what I have found and what happened initially, it doesn't SEEM like a timing issue. Wondering if anyone has had similar issue or is familiar enough with it to offer any advice. I am willing to replace the pcm or the timing, but want another opinion about the PCM as electronics like that are typically not returnable once you have used them. Appreciate in advance any suggestions or advice.

 

[Dennis_H]

I don't know what the issue is, but if you think it is the PCM, please in the name of sanity, do not send to Module Experts in FL. They say they test and repair PCMs, but will immediately tell you it is bad and you need a new one for a considerable amount of money. You are screwed because you don't know if they hosed it up, but you don't have one now and have to replace it... Lesson learned the $hard$ way.

 

[tstripe76]

Thanks Dennis for the heads up! Can't imagine how frustrating that was!

 

[Brandonian]

Not familiar with this deep in - but willing to give my .02 in hopes of helping!

One stupidly basic suggestion - what's your battery reading at if tested with a voltage meter?

The next step is I would get the alternator tested...the thing that leads me to point to battery/alternator is those are both circuit codes - and the alternator is what gives the juice, also the fact that if you let it sit and then go try to start it, it will get further in the turnover process but not turn over. My Commander - I mean it had a couple of prior small warnings that I may have ignored, but was driving home, lost all power, and was barely able to pull off the highway ramp to be clear of oncoming traffic, but it died died. Just right in the middle of intersection turning and bloop there she went.

I have had alternators going bad/go bad that do weird untypical things, and I have seen a few that throw odd random janky codes.

both of those are quick easy rule-outs..

have you checked your coil-packs?

Next up - time to check ground wires, if I recall there's a ground wire on the starter, and ground straps/wires below - should check those first? -

The next, remove your throttle body, clean it up and see if there's anything to bat an eye at with the connector pins in it, very doubtful but never know! .. If that's not the it, then I would do is disconnect the connectors on the PCM and the Throttle Body, and get the Circuit Cleaner (if you don't know what it is, it's next to the brake cleaner generally at the parts store) - and clean up those circuits, and make sure none of the pins are loose - if you have a loose pin you can probably re-pin it yourself. But these steps are doubtful, I have a feeling it'll be in one of the 3 above steps. Reconnect after cleaning and see where it goes.

If you've checked all these, then I am sorry - but just throwing some ideas .

regards,

 

[Brandonian]

Also REALLY stupid - but my wife did have a '99 Chrysler Town and Country that stopped starting due to a very dirty air filter...of course no codes popped up - it would turn over similarly to yours though and just not want to get going - I felt the filter looked ok, but obviously it wasn't - replaced air filter per the master dad's recommendations and it turned right over - so since you're already in there make sure your air filter is clean and clear - as little as it sounds, that could be a clear indicator...It would NOT explain the codes however - so likely not the culprit.

and yes - I'm a very backyard mechanic that only learns as I go haha :0).

 

[Dennis_H]

Not familiar with this deep in - but willing to give my .02 in hopes of helping!

One stupidly basic suggestion - what's your battery reading at if tested with a voltage meter?

The next step is I would get the alternator tested...the thing that leads me to point to battery/alternator is those are both circuit codes - and the alternator is what gives the juice, also the fact that if you let it sit and then go try to start it, it will get further in the turnover process but not turn over. My Commander - I mean it had a couple of prior small warnings that I may have ignored, but was driving home, lost all power, and was barely able to pull off the highway ramp to be clear of oncoming traffic, but it died died. Just right in the middle of intersection turning and bloop there she went.

I have had alternators going bad/go bad that do weird untypical things, and I have seen a few that throw odd random janky codes.

both of those are quick easy rule-outs..

have you checked your coil-packs?

Next up - time to check ground wires, if I recall there's a ground wire on the starter, and ground straps/wires below - should check those first? -

The next, remove your throttle body, clean it up and see if there's anything to bat an eye at with the connector pins in it, very doubtful but never know! .. If that's not the it, then I would do is disconnect the connectors on the PCM and the Throttle Body, and get the Circuit Cleaner (if you don't know what it is, it's next to the brake cleaner generally at the parts store) - and clean up those circuits, and make sure none of the pins are loose - if you have a loose pin you can probably re-pin it yourself. But these steps are doubtful, I have a feeling it'll be in one of the 3 above steps. Reconnect after cleaning and see where it goes.

If you've checked all these, then I am sorry - but just throwing some ideas .

regards,

My weird issue on my son's Escape was an alternator issue. Had a bad one, replaced with off brand and still had an issue. That's why I leaned to PCM. Mine ran though and caused voltage to spike to 18V and go crazy. You could charge the battery and unplug the alternator since it is accessible on an Expedition. The Escape, you get to pull an axle and remove motor mount to get to the alternator...

 

[Brandonian]

It's worth hooking up a tester and just checking the alternator that way - but it won't always identify a bad alternator. But I'd start with battery voltage, and then move to Alternator.
In the past my lights would Christmas Tree for a SPLIT second while driving - it was so easy to miss, and then a couple days later bloop - just die out.

A replacement alternator I got wet (had done the alternator, and a water pump with thermostat and radiator) - I took it to the wash and opened the hood and washed the living pooh out of it - didn't think anything of it, started it up and drove home, next day ****, no start lol. Got the alternator too wet and it burnt up. Yeap, backyard mechanic .

I'd still be hesitant on a whole PCM issue, there's got to be something finicky causing it if it was just driving and went kaput.

 

[tstripe76]

Brandonian - since i cant test voltage output on the alternator without it running, are you talking about just taking the alt to the part store to have it bench tested?

 

[Dennis_H]

Brandonian - since i cant test voltage output on the alternator without it running, are you talking about just taking the alt to the part store to have it bench tested?

My other son's F150 had a failing alternator that would test fine at the store. Seemed to work for 5 min after startup, then go to 0. It is worth a shot, but I don't trust the testers. Took it off 3x that evening and could do it in 10 min...

If you think it might be the alternator, start with charging the battery fully with an external charger. You can unplug the signal wires, not the charge cable, and still be OK. Those go straight to the PCM to control charging. If it is telling PCM there is an issue, maybe it prevents it from starting. It will probably throw a code, but the alternator is (supposed) to go into a standalone mode and charge at 14V without that plugged in.

 

[tstripe76]

Brandonian - ah, nice to know, I'll check the alternator and battery as others have also mentioned battery/alternator. Thanks for the tip on how to do it.

 

[tstripe76]

So battery is fully charged, sits at 12.4 volts. Disconnected the alt signal cable, but still no start situation. Tested both primary and secondary resistance on the coil packs, all are good. Disconnected the 3 harnesses that connect to the PCM, checked pins, reseated. Cleaned MAF Sensor with MAF sensor cleaner, and have followed the entire harness from PCM to all the different end destinations, if there are any breaks or issues, they are hidden, as its all still in the protective sleeve, no signs of melting or other compromise, nothing pinched, etc;. I also scanned again hoping to get another code to help, but instead the P1636 and the P2107 are now gone (i did not clear them). Still have P0103 and the 4 O2 sensor codes, but that should not cause no start situation. Going to check the throttle body, not sure what else to check. Is it possible that even though the crankshaft position sensor is reading and sending rpms, its still faulty and that might be the issue? Thoughts?

 

[Logan97]

I just bought a pcm from flagship one for my 07 expy. I'll let you know how it goes when I get it in case you still want to go that route.

 

[Brandonian]

Did you take the alternator for testing? - p1636, from the few moments I was able to look it up, can be specific to a low voltage - so disconnecting your alternator may have done that one! Could be another sign of an alternator issue - If you have not tested the alternator, I'd remove that and take it in, as I said the test is not a tell-tale sign as it could read good and still be bad (if you have a keen nose - you can sometimes more often than not smell if an alternator burned up by sniffing it up close, sounds really silly but I have previously fully been able to on the alternators that have burned up on me. Glad to hear the battery is reading 12.4volts, always worth checking the easier stuff before moving straight into more complicated lol.

I think this is electric related now...but since the codes changed I am hard pressed to believe the PCM is bad now - can never know from far away though .

 

[Brandonian]

Also follow your ground wires down below - not from the PCM up top - but check the frame area grounds. If there's a fault there it'll stand out.

 

[Brandonian]

sorry not sure why I looked up p1636 again, obviously I can't read...If the MAF sensor went bad - that's a fairly cheap and easy replacement - did you check your filter? Take that filter out and shake it really good and see where that gets you - I wasn't joking :0 .Lol

 

[tstripe76]

I did not have the alt tested, just disconnected the signal wire. The air filter is new, but I also disconnected the whole air intake on top amd still nothing. Usually with all that off it will run, it will be a little off without the maf readings but still start and run. I'll check the grounds umderneath.

 

[tstripe76]

So checked grounds, seem good, not broken, not corroded, not loose. As for the alt, if it was bad, wpuld disconnecting it resole issue (at least temp)? I know it wouldnt run long, but it should run right? Only ask because like was mentioned, it may still test good on the bench, so only way to know is to replace (or I like the idea of the sniff test). They are not cheap and hate just throwing parts at a problem.

 

[Brandonian]

Sorry - for some reason I don't get e-mails of new replies to a thread I've chimed in on lol.
I cannot give a "definitive" answer to that...with so many checks and electronics, I am inclined to believe if the alternator was not connected it would not start - because of all the electronics checks and balances contained therein of our lovely "modern" day computer controlled engine systems - the battery does not provide enough juice to run through all that.

I would still test it and see. Worth a quick look. But the code did change when you unplugged it and plugged it back in - so that's actually a hope that may be it. The grounds aren't typically something to look for that's why I became fixated on the alternator, and how it died while mid drive like it did.

Definitely don't throw parts lol - I would remove the alternator, sniff it good - and take it to get tested (however if you sniff it good and you can smell any burnt at all, you found your issue) - I would test it 2 places if the first one tests good (two different store front types like one at oreillys and one at autozone or something) just to be sure. Once that's ruled out we can move on with something different, I'll try to give this some extra thought.

 

[Steve Hartman]

I had this problem with my '07 Expedition! It would start for a second and then stop! Every time the same thing. What was it? It was an air leak in the intake from when the tune-up was done. The big rubber hose that goes from the intake line to the thingie that looks like a carburator (but ain't!) was smashed, came loose, and was letting a ton of air in! And even little ol' me was able to figure out that if the engine is suckin' air, it ain't suckin' gas! LOL! I'd look there, first! And let us know, would you please? Good Luck!

 

[Honocor]

I keep getting stuck on the O2 sensors. I had a mountaineer that did the same thing. After almost checking EVERY SINGLE fuse the 47th one iirc was blown. I never figured out what that fuse was for exactly but it prevented starting. Turned out one of my O2 sensors had a broken wire that was only held together by the plastic and when the wire shorted it blew the fuse and caused a no start. Took me about 3 fuses to finally figure it out.