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My wife's 2007 Acura RDX recently began throwing a "Check Brake System" message on her dash. After reviewing the diagnostic information, two codes are showing up, P16DB and P16DD.
I'm seeing some conflicting information and was wondering if anyone could guide me in the right direction. I have seen a few posts pertaining to a bad brake booster or bad brake booster relays? Has any one else experienced this or know where the relays are?
I have noticed that the brake pedal is starting to feel soft, but I replaced the rotors, pads, and fluid about 4 months ago and the brake fluid level is fine.
I could not be there unfortunately, but I had my wife stop into the dealership to run a diagnostic. I guess 3 fuses were corroded and the technician said that the fuse box was exposed to the elements. I'm not quite sure what that means or where these fuses are located, but I'll have to do some investigating tonight. She thought he said that the fuse box was dangling near the wheel well? I have no idea what that means. Again, I'll have to look tonight.
Also, it appears there is an issue with with the Electronic Brake Vacuum Pump. They did not elaborate as to what the problem was (leak, broken, etc.), so I may have to also investigate this later tonight. Based on the below, does anyone have any ideas?
I just don't want to call back and sound like an ignorant
So, I ordered a 5-pack of new OEM relays for like 11 bucks and will replace them upon arrival. If replacing the relays does not remove the codes, then I will start looking into the pump assembly.
I'm still confused as to what the technician was trying to say when he mentioned that the fuse box was dangling? Lol, I think he was trying to pull a fast one over on my wife . We will see what I find when I get home tonight.
Hypothetically, if I replace the relays and the "Check Brake System" light goes off, does anyone know if I still actually have to clear the OBDII codes? I'm not sure exactly how our 1st generation RDXs stores codes. Obviously each make and model is different with the data stored on their computers.
I'm hoping that the only problem is the corroded relays. Let me know if anyone else has any thoughts with this approach.
Those are located in the engine bay next to the computer behind the intake on the driver side of the hood. They should have a cover that clips on the fuse box case and it shouldn’t move at all. I’ve never heard of fuses on our trucks corroding like that before as well as the fuse box dangling by the wheel well...
I know the Acura dealership is expensive but honestly compared to the service I got at the local jiffy lube or mavis discount tires I was happy never to look back and only take my RDX to the dealership I got it from every time.
I’ve heard of people taking their RDX’s to Honda dealerships on his forum and not getting results that make sense to me.
You have to understand buying a more expensive car with high mileage you have to have to means to take care of it.
If you can’t figure it out take it to the Acura dealership get a quote check it yourself and come on the forum. At least you’ll get a year warrant for parts as labor at a dealership.
Trust me I had plenty of family members get fleeced by the local guy looking to do a quick job at the local shop. Sometimes the Acura dealership is the better choice...
So, I ordered a 5-pack of new OEM relays for like 11 bucks...
Hi!
That sounds v cheap, nice, mind to post a link?
Am about to order 3-4, looking for Mitsuba relays and cheapest i could find is around 10$: 2 years ago did not realize the significance having in the relay box (which I changed) 4 other relays identical to the reported failing A.C. relay "-A01" so I am playing catchup again.
I know the Acura dealership is expensive but honestly compared to the service I got at the local jiffy lube or mavis discount tires I was happy never to look back and only take my RDX to the dealership I got it from every time.
I’ve heard of people taking their RDX’s to Honda dealerships on his forum and not getting results that make sense to me.
You have to understand buying a more expensive car with high mileage you have to have to means to take care of it.
If you can’t figure it out take it to the Acura dealership get a quote check it yourself and come on the forum. At least you’ll get a year warrant for parts as labor at a dealership.
Trust me I had plenty of family members get fleeced by the local guy looking to do a quick job at the local shop. Sometimes the Acura dealership is the better choice...
Honestly, I don't think it's fair to classify all Honda dealerships as sub-par to Acura dealerships. It's all about the people that you are working with. The Honda dealership near my home is top-notch and they have excellent reviews. I don't usually take my vehicles to ANY mechanic shop unless I am unable to diagnose my own problems. My OBDII scan tool recently broke and I do most work myself (all fluid changes, filter replacements, pressure switch replacements, coilover installations, endless money-pit modifications, etc. lol). If I do run into a bind, I bring my 2005 Acura TL and wife's 2007 Acura RDX to my local Honda dealership, because I trust them. They have excellent ratings and have ALWAYS treated me fairly and with class. A friend of mine is a technician that works there and he is always 100% honest with me. Unfortunately, he didn't have any gaps in his schedule the other day, so my wife met with someone else.
Upon further review, the technician actually did know what he was talking about. I found the following diagram in the owners manual. There is a secondary fuse box next to the battery.
I actually called the technician and he explained to me that the bracket holding the secondary fuse box looks like it became detached and the fuse box was being exposed to the elements near the wheel well. When my switches arrive this weekend, I will look into this further and share my experiences. To go the extra mile, the technician told me to call him on his personal cell phone if I run into any issues when trying to replace the relays since this is not a common fuse box location (and many people miss this). I shouldn't have been so skeptical.
I'm glad that we brought her RDX into the shop, because there is not much information online (Acurazine or other websites) , regarding these codes for our1st gens. Here's to hoping that the issues will be resolved once the relays are replaced.
Originally Posted by Altair
Hi!
That sounds v cheap, nice, mind to post a link?
Am about to order 3-4, looking for Mitsuba relays and cheapest i could find is around 10$: 2 years ago did not realize the significance having in the relay box (which I changed) 4 other relays identical to the reported failing A.C. relay "-A01" so I am playing catchup again.
The link shows "-A03".
I may end up ordering the "-A05" despite being though more expensive, which it's not made by Omron, as replacement for fan relay.
The secondary fuse box is indeed located next to the battery on the driver's side.
Here are a few pictures that show the amount of corrosion on each of the relays.
I used a few cotton swaps and CRC Electronic Cleaner to clean out the secondary fuse box before installing the new relays. After about 10 minutes, the RDX was back together and operating without any Brake System lights. Wohoo!
The original part number for the relays is 39794-SDA-A03, which is manufactured by OMRON in the USA and is still listed on many OEM Acura websites as the correct relay. The upgraded replacement part number is 39794-SDA-A05 and is manufactured by MITSUBA in Vietnam. I believe this is what many of you are referring to. However, please keep in mind that the "upgraded" relay is only in reference to the sticking A/C clutch. To my knowledge, you should not simply replace all A03s with A05s. Here is a thread that describes the upgrade:
In the future, if I have any issues with these relays, I can upgrade to A05s potentially. However, I wanted to follow Acura's current recommendation and for $11 I took the risk.
03-04-2019, 12:22 PM
. We will see what I find when I get home tonight. 
