[Rogue6]

2014 Accord Sport with CVT. 97K miles, well serviced, runs flawlessly.

About a week ago I was running home to grab something, so I left my car idling in the driveway to run into the house and grab the thing. Came back out after about two minutes and suddenly had three warning lights on my dash: Power Steering, Traction Control and TPMS.

The power steering works fine, as far as I can tell the TC does too (hard to test that), and all of the tires are at regular pressures. To knock out an easy one, I tried calibrating the TPMS but it either gives me a 'failed to calibrate' or it seems to start calibration but never clears the TPMS light. From my perspective, there is absolutely nothing malfunctioning with any of those systems. Over the following week the lights have come on intermittently, with the only thing seeming to trigger them is when the car has been running and fully warmed up for at least 20-30 minutes. They don't come on during short trips.

I bought an Ancel AD310 Classic Enhanced OBD2 scanner and have been driving with it plugged in reading live data every trip, patiently waiting for two days for the MILs to come back on. They finally did today while driving home after having waited in the drive through for a while (suggesting again it only happens when the car's been on for >20-30 minutes). But even though I'd had the scanner plugged in and reading live before the lamps came on, it will not read the codes.

I tried every combination possible of plugging in the reader with the car off first, ignition on but engine off, engine on already, etc. Codes are on the dash but they can't be read by the scanner. I tried using the scanner to clear the codes but of course it gave an error since it hadn't read them anyway.

Any ideas what could trigger those three seemingly unrelated warning lights?

Any idea why the scanner may not be able to see them even when they're on?

 

[Miker]

How old is the battery ? A low voltage on the battery during an OBD2 scan may cause the OBD to not connect.

All those lights are also indicative of a low voltage.

During the idling somehow the voltage dropped and lost connection with the module that controls those TPMS,TCS and possibly the power steering (electrical assist) system. They are somewhat connected in the fact that if the module recognizes a low tire pressure it shuts off VSA and TCS. PS may also be showing a problem if the battery voltage is low.

Although the battery seems strong enough to start the engine it may be having a problem with keeping a high enough voltage to the ECU and other modules.

Charge the battery and try to rescan the OBD.

 

[Rogue6]

Thank you for the reply! The battery isn't very old, changed in December of 2019 so it's just over 2 years at this point. What sort of voltage should I be seeing? I just took a short drive after the car had been cooling for ~2.5 hours. No warnings again. Plugging in the scanner it reads ~12.2V before I start the engine, and about 14.2V after starting while idling. After I got back home and shut the engine off, voltage was down to 12.0V. That's probably low, right?

I should have been clearer about the OBD2 scanner not reading the codes. The scanner connects fine, and shows all of the live data you'd expect both before and after starting the engine. It simply doesn't 'read' that the lights are on the dash, which is... upsetting.

Ok, I got a chance to measure the battery directly at the terminals with the car off and I'm getting 12.7V, so that's looking much better than what the scanner was reading. Not sure where it takes that measurement.

 

[03LXV6]

I don't think your scanner is capable of reading the codes your car is showing. Your issue is probably just related to single sensor but most systems are tied together so once you get a code for one, they are all affected. I don't recall if the 2014 uses in wheel TMPS or ABS sensor but that could be the root of your issue and would cause VSA to also malfunction.

 

[Rogue6]

Thanks again for the replies. You guys are awesome.

Yeah, it seems like it's only capable of reading faults that are there when you key on. These only appear after starting the engine.

So do I just need a better scanner, or is this going to require taking it to the dealership and getting the full diagnostic test? If they're going to charge me $100+ just to scan it and tell me it's a faulty TPMS sensor, or I can buy a higher end scanner for the same(ish) money, I'm fine buying the better scanner and returning this one.

 

[Schwarzes]

Thanks again for the replies. You guys are awesome.

Yeah, it seems like it's only capable of reading faults that are there when you key on. These only appear after starting the engine.

So do I just need a better scanner, or is this going to require taking it to the dealership and getting the full diagnostic test? If they're going to charge me $100+ just to scan it and tell me it's a faulty TPMS sensor, or I can buy a higher end scanner for the same(ish) money, I'm fine buying the better scanner and returning this one.

Hi @Rogue6, your 2014 should not have in-wheel TPMS sensors. My 2013 has no sensors. This generation of Accord uses the ABS sensors to infer a low tire.

 

[Rogue6]

Hi @Rogue6, your 2014 should not have in-wheel TPMS sensors. My 2013 has no sensors. This generation of Accord uses the ABS sensors to infer a low tire.

So does that mean it's a bad ABS sensor? If so how can I diagnose that/figure out which one? I thought there was a different warning light for ABS vs TPMS, so wouldn't I see an ABS light if a sensor were bad?

 

[glen e]

12.0 is a 50% charge level.

 

[Rogue6]

12.0 is a 50% charge level.

That was the measurement the scanner was giving. When I checked the battery with a multimeter directly at the terminals it was 12.7V.

 

[Schwarzes]

That was the measurement the scanner was giving. When I checked the battery with a multimeter directly at the terminals it was 12.7V.

The multimeter could be measuring higher because the battery still has surface charge. Try turning some lights on to remove the surface charge and see if the voltage drops a few cents, to closer to 12.0 V.

 

[Rogue6]

The multimeter could be measuring higher because the battery still has surface charge. Try turning some lights on to remove the surface charge and see if the voltage drops a few cents, to closer to 12.0 V.

OK, just tried this on my car. Voltage before I did anything was 12.7V still. Turned the headlights on (car still off) and the voltage dropped to 12.02V. Turned the lights back off and waited a few minutes and the voltage had recovered back to 12.68V.

To give a comparison, we just replaced the battery in my wife's 2018 CR-V two weeks ago (on the same day my problems started). Her battery before doing anything was at 12.5V, and dropped to 11.9V With the headlights on. So it really doesn't seem like my battery is causing the problem.

 

[OmegaSupreme]

I'd start with replacing the battery. Its easy to replace and can cause the most issues.

 

[Schwarzes]

So does that mean it's a bad ABS sensor? If so how can I diagnose that/figure out which one? I thought there was a different warning light for ABS vs TPMS, so wouldn't I see an ABS light if a sensor were bad?

So with the voltage test out of the way, back to your sensor question: if an ABS sensor was faulty I would definitely expect to see a code in the scanner. The issue might be in the electrical system instead. Specially because the power steering light turned on too.
Another question: when you left it idling and then the warning lights came up on the dashboard, was the climate system running? Was the AC engaged in AUTO?

Disclaimer: I'm not a mechanic, just technically inclined and trying to follow some logic.

 

[Rogue6]

So with the voltage test out of the way, back to your sensor question: if an ABS sensor was faulty I would definitely expect to see a code in the scanner. The issue might be in the electrical system instead. Specially because the power steering light turned on too.
Another question: when you left it idling and then the warning lights came up on the dashboard, was the climate system running? Was the AC engaged in AUTO?

Disclaimer: I'm not a mechanic, just technically inclined and trying to follow some logic.

No, when it was idling in the garage the A/C system was completely off. It was a mild day outside, so I just had the windows cracked a bit.

I've continued to carry the scanner with me in the car and plug it in from time to time since I first posted. On the occasions where the codes come up, it still doesn't read them. To reiterate, the codes are never there before the engine is started. They only come on after the engine is running.

I've also noticed that in the last week when the outside Temps here have dropped, the codes have come back less. Not only does it seem to be triggered only when the car warms up, but it also seems to be more likely to present when it's a warmer day outside (which could simply be because that warms the car up faster). It's supposed to be cold the next two days, but back into the 70s on Wednesday. Maybe it'll come back again then.

 

[2Accordz]

Your battery isn't holding a charge as it should be..supposed to bear at least 14.4V under load, I believe.

 

[Rogue6]

Your battery isn't holding a charge as it should be..supposed to bear at least 14.4V under load, I believe.

I'll check it at the terminals with the engine running later tonight when I get home. My first voltages posted were read from the scanner, but it seems to read quite a bit lower than the voltage at the terminals. Not sure I'd trust those original values anymore. If anything it seems to be a healthier battery than I originally thought.

 

[sequoiasoon]

A couple things. Your ground from the battery is attached with one bolt (maybe 2) to the inner fender. Many electrical issues are caused by a poor ground. The area is painted so only contact is the threads of the bolt that cut through the paint and they rust. Many mechanics will clean that up with bore wire brush, tap and clean paint where it contacts, Coat lightly with a conductive paste (like Kopr-shield) or dielectric grease then reassemble. Happened on my sons Kia. Rusted bolt snapped trying to remove. had to drill and re-tap. He had lots of issues, horn, lights flickering, radio reset. Fixed ground connection and all issues went away, same battery that was testing good the whole time.

Your alternator is also variable output so unless it sees a load reduces output so you get better gas mileage. If you want it to charge especially with short trips around town, turn on your headlights or rear defroster. Multiple threads on the charging because of that. A/C and fan might not be enough load.

My '19 Pilot is the same way. Brand new battery and is staying around 12.2V with no load even on a 1.5 hour long trip. Turn headlights on and it's 14.2V, even front and rear AC on high and seat heaters are not enough to draw the extra or tell ECU it is a high demand.

 

[Miker]

A/C is not enough to get the ELD to output more voltage as you've seen. If you have a "meter" in the cigarette lighter plug (power port) the reading will be lower because there is a HUGE voltage drop through the very small gauge wire going to the port.

Second, the ECU ALWAYS reports a very low battery voltage (as I have seen) for probably the same reason of small AWG wire going to the ECU. I usually get 11.9-12.1 VDC when doing a live data dump from the OBD port.

But the battery at the posts measures 12.6-12.8 after the surface charge is depleted as @Schwarzes mentioned.

 

[Schwarzes]

Many electrical issues are caused by a poor ground.

👆 I would check this next

 

[greg1c]

The battery connections all need to be clean and tight. The way the system knows current draw is through the sensor on the negative post on the battery. The alternator is controlled by the ECM with a serial protocol called LIN. Read this article, but there is no longer an ELD in the Accord since the 9th gen.

Honda LIN Line Controlled Charging Systems

On older vehicles, the alternator and engine were never really connected. The alternator was internally or externally self-regulated to a voltage, but that was it.

www.underhoodservice.com

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