2013 Mazda5 AT Power loss, No CEL and Throwing Codes

[whizbo]

My 2013 Automatic (140,000 miles) has started developing some odd behaviors.
When driving, while not accelerating/decelerating, the engine sounds muffled and feel sluggish. If I punch it, the Transmission drops a gear and the engine has it's normal pep. There is no CEL, but it's throwing lots of random codes: P0481, P0505, P0661, P0662, P1260, U3000, P0744, P0751, P0752, P0753, P0756, P0757, P0758, P0761........ The list goes on. My Favorite is P1260 - THEFT Detected, Vehicle Immobilized. If I clear the codes, it seems to go longer before throwing them again with the AC off. Watching the OBD voltage with a scanner it varies between 12.7v and 13.8v. There is a definite dip when the AC clutch engages. Recently it has started hesitating to turn over when starting. Interstate tested the battery, and told me it's good. Advanced Auto tested battery/alternator/starter and told me the battery is bad, the alternator good, and with a bad battery they can't tell me if the starter is good or bad. The employee didn't seem very comfortable with the testing tool. So.... maybe the battery is bad? I'm not monitoring gas mileage, so I can't speak to that. Within the past 6 months I replaced the TCM because the old one was starting to put me in limp mode due to heat soak. I have also recently (past 6 months) replaced the plugs, cleaned the MAF, new air filter, power steering fluid, the front shock assemblies, but I doubt those are related.
I plan to put the old TCM back in to rule that out. Any other thoughts? Maybe AC clutch? How would I test the AC clutch?
Isn't electricity fun?

 

[whizbo]

I should also mention that I've always felt like the engine bay in this car is hot. Coolant lives right around 190degrees, and the car hasn't thrown temp warnings in the past. I'm concerned that I might have some wiring harness damage due to heat? Or maybe I'm just paranoid about heat after the TCM failure.

 

[edmaz]

.... Watching the OBD voltage with a scanner it varies between 12.7v and 13.8v. ...

Try testing the voltage with a multimeter attached to the battery.

 

[whizbo]

Battery voltage was low with the car off, so I replaced the battery. It's starting consistently now, but still throwing that huge list of codes. The car seems to run fine until it warms up (~10 mins) then I notice that muffled/slugish behavior, and that's when I get all the codes.

 

[edmaz]

You mentioned previously that running voltage was as low as 12.7, so what are the readings now with the new battery? And while you're testing at the battery, check for excessive ripple by switching the meter to the A/C voltage setting, and see what the voltage reading is, both at idle, and also around 2-3K RPMs. It should be a very small fraction of a volt.

 

[whizbo]

12.5V at the battery when off. 13.7-8 at the battery while running. 0.010 to 0.014 V A/C while idling, and the same at 3000RPM. Note: This is after the car sat for awhile. I'll test again tonight after my commute, when the car is warmed up.

 

[edmaz]

All of those readings are normal, so it would appear that the charging system is ok. That large variety of codes, particularly the transmission ones, IMO suggests a problem with one of the big wires or something inside of the fuse box, so you might want to first take a look at the condition of the primary ground wires, and also if their connections are solid and paint/rust free. Then, if the ground wires are ok, a look at the underside of the fuse box and the power wires connected to it might be a good thing to check.

 

[negusm]

Get a wiring diagram and check all your GROUNDS. This could be a bad ground somewhere affecting the PCM.

 

[edmaz]

Get a wiring diagram and check all your GROUNDS. This could be a bad ground somewhere affecting the PCM.

The PCM does not set those lower level transmission codes posted here - it's the TCM which does that. So the issue with this vehicle has to be more global than something pertaining only to the PCM. However, it also appears that the OP has probably left the building, and that we'll never find out what the actual root cause turned out to be.

 

[whizbo]

I'm still here, and I appreciate the help! Life has gotten a little crazy over here, and since this issue isn't throwing a CEL or stranding the car it's priority has been temporarily demoted. I likely won't get back to it until this weekend at the earliest, but I will check the grounds and follow up.

 

[whizbo]

I checked the ground points at the battery, body near the battery, starter, and alternator. They all look good. I assume there are other grounds I should check, but I don’t have a wiring diagram, can anyone point me at one? The positive cable from battery to fuse box looks good, and I can’t find any damaged wires coming out of the fuse box. Some more info, my obd app is showing an emissions test fail for the o2 sensor and Evaporate system. Even before the random codes are thrown. Note, I still haven’t seen a CEL during this whole ordeal. Maybe this is two unrelated issues? The o2 sensor is causing the sluggishness? And in addition to that i have an electrical issue causing random codes? Or maybe it’s the bad o2 sensor shorting the electrical? Finally, I know there are two o2 sensors, would an emissions test point to either one specifically?

 

[edmaz]

.... Note, I still haven’t seen a CEL during this whole ordeal. ...

Something that I just assumed about that, but I should have asked if all of these random codes are marked 'pending' on your reader display. I was thinking that all of these codes were just pending and getting erased fairly quickly by the PCM in a repetitious cycle, which would explain why there is no CEL. So do you see the status of pending on all of them?

 

[whizbo]

Not pending… but “Test not completed since last DTC clear” and/or “Test not completed during this operation cycle”. Which might be the same as pending? All have the second note, some have both notes.

 

[edmaz]

Those test not completed messages come from the monitors, and are not directly related to codes. The CEL not coming on for non-pending codes is definitely an abnormality, unless it's simply just a burned out light bulb. So does the CEL light up as it should when you turn the key or push the start button to 'ON'?

 

[whizbo]

CEL bulb is working. Also attached a screenshot of some of the diagnostic codes on my scanner app. The DTC codes do not persist after the car is turned off. It’s a clean slate at engine start, and the codes only return after some driving.

 

[edmaz]

OK, first I'll correct what I wrote about the status messages. Without seeing that display, I just assumed it was the standard monitor messages, but the status messages in your pic definitely correspond to the codes. That said, those messages make just as little sense as the boatload of codes, none of them turning on the CEL, and all of which are gone at the next vehicle start.

Although the primary grounds and big power wires can't be completely eliminated, it's probably best to set them aside in order to reconsider the charging system. You mentioned that this issue doesn't kick in until it's been on the road for a while, and that the A/C might be something of a trigger. So one diagnostic step would be to know what happens when you take the vehicle for a typical drive, but never turn the A/C and blower on. Have you tried that yet, so see if all of these symptoms happen anyway, even with none of that running? If you haven't tried a no-A/C trip, and it wouldn't be unbearably uncomfortable, I recommend running that test.

One possible thing that could be in play here is an alternator rectifier diode that's on the way out, and currently shows symptoms only when it gets hot and possibly also with a load applied to the alternator. So the idea is to take the load out of the mix first and see what the result of that is. I'm also not dismissing your idea about the A/C clutch having problems, which could mean this is some type of combination deal.

 

[whizbo]

A couple weeks ago, it was in the 90’s here and I drove with the A/C off. The codes still showed up, but I felt like it took longer. This afternoon it’s cool here (60F) and rainy. I wanted to warm the car up, get the codes, and then have the alternator checked. I drove around with the A/C full blast to heat up the engine asap. The parts store test says the alternator is good. After that, I cleared the codes, and drove around with the A/C off, and didn’t get the codes. Eventually I hit the A/C again and the codes returned. Your alternator theory is interesting. I’m not sure how thorough the in vehicle alternator test is. Any idea if that would catch the rectifier diode on its way out? Would it be worth the effort to pull the alternator for a bench test?

 

[edmaz]

The results from those tests that you ran is interesting, and the first one you described appears to eliminate the A/C compressor as the root cause. It's always hard to say how much a bench test can diagnose, and if heat is added as a failure factor, it becomes even more questionable.

What's happening with your vehicle is a REALLY strange set of symptoms, and I have to say that excessive ripple keeps on coming back to me as a possible explanation for what's happening. AC voltage will drive an automobile DC system crazy, and it's easy to imagine all of those wacky codes being set if excessive AC is being produced. I'm of course not certain of that, just that it fits these bizarre symptoms very well.

If I had this problem on one of my vehicles, I'd attach a multimeter to the battery using leads long enough to reach comfortably into the cabin. I don't know your vehicle at all, but most of the time there's a way to snake wires through the firewall via some port or hole that's already there. Then, with the meter temporarily taped in a position which is easy to read safely, the voltage can be monitored while driving. With your vehicle's symptoms, I'd start with AC voltage monitoring, but the meter can of course be switched between AC and DC any number of times. With a setup like this in place, it would also be possible to switch the leads to the alternator instead of the battery, in order to monitor what the alternator is actually producing, without being smoothed out by the battery.

Other folks would likely go at this using a different approach, and almost any type of diagnostic testing is fine in my book, versus just throwing parts.

 

[whizbo]

I've been driving around the past couple of days with my Multimeter tied into my battery. These tests have been with the Air Conditioning Blasting. The highest AC voltage I've observed is 0.187V. DC voltage is a strong 13.9V while running. Note: I'm just observing the values on the meter "manually" so if things are happening faster than the LCD refresh rate, I would miss them. The outdoor temps have been lower the past couple of days, and the car is not as quick to throw codes as it has been in recent hotter weather. However, It has still thrown the codes. I have noticed that the Muffled/sluggish behavior isn't tied to the codes. It can be Muffled/Slugish, and not have any codes. So, perhaps this is two unrelated issues. One electrical (the codes), and one.... something else engine performance related. I'm going to keep the meter attached for the near future with the hope that I get some hotter weather to see if it increases the frequency of codes. Any thoughts on tests I could run for the Muffled/sluggish behavior?

 

[edmaz]

Good to read that you ran that voltage testing, but disappointing of course that it didn't confirm a bad diode in the rectifier. Not surprising though that this problem won't be giving in without putting up a big fight. And what you wrote about the speed of electrical events versus the speed of the meter is definitely true, so nothing should be ruled out just yet. And another yes to the possibility of there being two (or more) separate problems.

So perhaps it would be good to take a look at the performance side of this. Do you feel the performance of the vehicle switch from good to sluggish, back and forth during a typical drive? Or is it more like once it becomes sluggish, then it remains that way until the next trip? Also, do you have your ODB live data reader pinned up on the dash, so that you can read it safely while driving?