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Discussion Starter #1
So last night my wife gets home and greets me with "there's something really wrong with the car!" crap....

So she tells me that when she's about a block away from the house at a stop sign "all the lights came on" and the vehicle accelerated very slowly.
The way she described the acceleration was as follows:
She was driving in our residential neighborhood starting from a stop sign when she added the desired throttle (normal acceleration to ~25mph)
Initially the vehicle accelerated only to about 5mph (sounds like idle speed to me)
She added slightly more gas with no effect
She released the gas momentarily, then re-engaged the gas to normal acceleration amount - within 10-15 seconds the vehicle resumed normal acceleration
At every stop sign (there were 3-4) this cycle would take place after having come to a stop and re accelerating
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When this happened she said the Check Engine Light, VSA Light, and Tire Pressure Monitoring System lights all came on.
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She did not notice any abnormal noise or vibration.
When she got home she shut down the car, came and got me. I got in and started the car, no lights were on, everything sounded normal. I drove around the block and had no issues.


To me this sounds like the vehicle went into limp mode for some reason. So I got the OBD scanner and pulled the following codes.
P030x(0-6) - Random Cylinder Misfire + Mifires on each individual cylinder <<<I've had these intermittently for awhile
P2138 - Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
61 - Power supply voltage failure information: Low or High Voltage
83 - ECU failure information: PGM-FI Relation Failure
11 - Front right tire low air pressure
15 - Rear right tire low air pressure
The random cylinder misfires have been an ongoing thing I've been troubleshooting, but to date there has never been any adverse effects associated with them. So far I've tested coils and replaced plugs. I read somewhere that using non-factory oil filters can cause this on some pilots, so I was going to use a factory filter on the next oil change which is coming up soon. If it continues the next plan was a valve job - but it's VCM and I really don't want to do a valve job.


With the power supply voltage failure I'm wondering if it's a relay/alternator/battery that's nearing the end of its life and the transient power issue was the course of the rest of the codes?


Any ideas from you guys on ways to troubleshoot? I'm off for the next two days and would like to leave my wife with a vehicle we are confident in when I go back to work.
 

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I would start by inflating tires just to get rid of the noise in the codes.
Did you check the voltages with the engine off and on?
 

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Discussion Starter #3
yeah the front right was 28psi - it has a slow leak, the rest were 37-38psi. not really worried about the tire pressure though.

What i did notice that is concerning to me is that the oil level is very low. It barely registers on the tip of the bottom of the dipstick. The vehicle currently has 15% oil life remaining, although i'm headed to the store in our other car to do an oil change right now having noticed this.
This vehicle hasn't consumed noticeable amounts of oil in between changes in the past.


From searching the internet I have seen posts where these symptoms (limp mode) were caused by low engineoil pressure which makes sense.

I'm concerned that the engine has been damaged since it put itself into limp mode. No abnormal sounds, vibrations or temps though.
 

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Did you check the intake air duct for cracks typical for the age and mileage? If it's cracked around the clamps you might have a significant vacuum leak and actually dust might enter the intake through the cracks.

Are you on high-mileage oil? You should be.
 

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Discussion Starter #5
I'll check it, I use Mobil 1 Full Synthetic for oil changes. I think I may need to deactivate VCM, from what I'm reading high oil consumption and random misfires are common issues that arise from VCM.
 

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Discussion Starter #6
Well I changed the oil tonight, it was about 2 qts low. I put in Mobil 1 Full Synthetic high mileage and swapped the filter.
I also order a VCM Tuner II.
 

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Discussion Starter #7
So with the oil changed and codes reset i did a quick test drive and all was good.

However, wifey just called and she said the same lights came on as she was arriving at her destination about 25 miles away. She doesn't know if it went into limp mode or not as she was pulling in to park when the lights came on and so just shut the car off.

I'll pull the codes when she gets back and check the voltages.
 

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Discussion Starter #8
So she got back and the following codes were present (I had cleared codes after first event):
P2138 - Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
61 - Power supply voltage failure information: low or high voltage
83 - ECU failure information: PGM-FI relation failure
I tried driving around myself after she got home but I couldn't reproduce the issue.

I did the following electrical checks:
Battery Voltage: 12.57V while vehicle shutoff after being shutoff for~2 hours
Battery Voltage: 14.16V ON, accessories off
I then turned on all accessories (radio, seat and mirror heaters, a/c fans high, all lights, phone charger)
Battery Voltage: 12.51V accessories ON
seeing this voltage drop along with the associated codes I thought that the alternator might be about to go and that the issue might be from the battery eventually getting too low resulting in a transient undervoltage.
So I left the accessories on for ~20min, at which point the battery was at ~11.5V. I then drove the vehicle around again
After ~20min stop and go residential driving, I still couldn't reproduce the problem. The battery V had increased back up to ~13.87V.
 

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How old is the alternator?
 

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Discussion Starter #10
I just went through our records on the vehicle and it has never been replaced. The battery is nearly 4 years old. I keep the connections nice and clean though.

The alternator just shit the bed though haha.

Went out to start it up and nothing - hooked up a battery jump starter, it started up on the second try - but quickly died. Started again and gave it a little gas to try to get the alternator some more juice - but quickly died again.

Sounds like I'm ordering another alternator. Honestly relieved that it happened with me at the house, not with my wife and kids while I'm at work or something, and replacing an alternator isn't the worst thing in the world.
 

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Had there been a whine matching RPMs recently? That's often a sign of an alternator about to ? the bed, as you put it.

(Hey look, admins, I used one of your new and improved emojis. Still waiting for the legacy ones to be restored, though.)
 

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Discussion Starter #12
No there was no indication that it was having issues until this specific issue started a couple days ago.

My ac compressor had that whine as the bearing was worn a while back but i've long since replaced that bearing.
There are no abnormal noises or vibrations.
 

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Discussion Starter #15 (Edited)
The new alternator is in, but the battery is dead.

Once I jump it, it drives around no problem. I left it running for awhile with accessories off to get some juice in the battery. As soon as i shut off the engine, the car won't even engage the automatic door locks. Voltages are ~14.5V running with accessories off. Once I turn off the car the battery is at 12.1V

So tomorrow I'll put in a new battery, reset the codes and the VSA and we will drive it around to check - but I think it's going to be solved. The battery is about 4 years old living in the heat anyways, I'm sure all of this abuse just pushed it over the edge.

I also got one of those VCM killers that I'll install tomorrow just in case.


On a related note - I strongly recommend a battery pack jump starter for your car. Those things are amazing.
 

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Discussion Starter #16
Battery replaced and all is well, codes all reset and nothing has popped up so far.

It seems it was all just electrical issues stemming from a failing alternator.
 

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Discussion Starter #17
Well, unfortunately the problem has reared its head again - it appears it was not as simple as an alternator and battery replacement.

At least this time it happened while I was driving so I got to witness it.

So VSA lights come on, along with CEL (which was already on due to random misfires).

When this happen nothing is noticeable until the car comes to a stop - acceleration is then extremely sluggish until ~20mph where it then picks up a bit.
As the car is coming to a stop ~5mph, decelerating it has a rough downshift as it slows to a complete stop.

Shutting down the vehicle and starting it back up again causes the problem to completely go away with no noticeable issues whatsoever.

I keep an OBD scanner in the vehicle, so I was able to scan the codes while the issue was happenning, before I shut it down:
P030x - random cylinder misfires on all cylinders - has been intermittent for some time.
P2138 Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
61 Power supply voltage failure information: low or high voltage
83 ECU failure information: PGM-FI relation failure
112-1 Circuit failure information 2: Internal power source of ECU failure
Anyone have any experience with these issues? I'd appreciate any help or advice!
 

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Discussion Starter #18
Another related question - i'm reading in the ervice manual about P2138, step 5 says:
"Check APP SENSOR A and APP SENSOR B in the DATA LIST with the HDS."
Is this something I can do with a multimeter, or my OBD II scanner?

I'd really prefer to stay out of the shop if at all possible.
 

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APP sensor should be merely a resistor. At least it is in my Nissan. When I had a APP sensor failure I res-soldered all joints on it and it was fine for many years.
If that fails I would start by buying and replacing all fuses and re-doing all grounding points under the hood and then tried another ECU.
 
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