2017 CX-5: CEL P0847 - No Performance Issue - Dealer Wants New Transmission 8k

[pallor]

Hello.

I am seeking some guidance on the resolution of my issue. I have a 2017 CX-5 Touring FWD (manufactured 7/2017). Mileage is 120k. I have been the only owner.

While driving home this week the Check Engine light came on along with the AT, SBS, and TSC. I did not notice performance issues. I drove home and parked. I restarted the vehicle. Only the CEL came on. No other lights. The next morning I drove to my Mazda dealership for service.

The dealer determined that the P0847 Oil Pressure Switch 2 Circuit Low was the "issue." Their fix was to replace Switch B for $1000, but explained that what I really needed was a new transmission because as they said replacing the Switch would cause slippage due to contaiminaed fluid. The cost for a new transmission from them is $8000. (It is important to add that they did not check my transmission fluid in the inspection. This is a codes diagnostic only.)

They also suggested the patented myriad of things such as every tune up including replacing my wiper blades.

I went to AutoZone and had the code read. Still P0847. Also bought my own OBDII.

In researching I found a TSB on this matter: Service Bulletin Based on that, it appears the suggested fix is to replace BOTH switches (and I assume the ATF because it has to be opened).

I have sent off for Blackstone test kits to see how bad my ATF actually is.

Has anyone here had this issue successfully fixed? And if so what was the actual solution - eg. switch w/ drain and fill cycle or full transmission replacement.

Thank you!

 

[Jmaz]

If it were me I'd run far away from that dealer.

 

[sinistriel@]

Do you have any other codes or just the P0847? I would take it to a reputable local transmission shop and have them look at it. It's usually the switches failing. Diagnosis would be to remove the pan and inspect the type of debris in the fluid, pan and what is stuck to the magnet. They can test the switches to see if they've failed. Often times its a simple switch failure, if you have a lot of debris it could be stuck open due to that. You would then need to go deeper to find the source of debris.

 

[AL Cx5]

I'm assuming that you cleared the code and it came back?

Have you checked your trans level?

Does the fluid look dark and smell like it's burnt or different than fresh ATF?

Have you serviced the trans in the past 120K?

Since it's shifting correctly, I would be surprised the trans is hurt.

From the attached article replacing a trans fluid pressure switch can be performed by removing the pan.

I do 95% of my own maintenance. I would have the car on jack stands, drain the ATF, remove the pan and see if I could get to the pressure switch without removing the valve body. At that point, replace the pressure switch on the valve body, trans filter. Basically through some parts at it so I didn't have to drain the trans and drop the pan buy one time.

Since I do my own work, I over maintain. On our 09 Honda, I change the ATF every 10K and the trans filter at 100K. On the CX5T I'll change the ATF every other oil change at 15k and the filter at 100K or sooner. The hardest part is removing the belly pan.

It could be the trans filter needs to be changed. It has collected clutch material and has high pressure drop across the filter and throwing a code. You could change out the trans filter, add new ATF and see if this is the fix.

As mentioned, look for your self to see how much material is in the pan and take a pic and post it.

Used trans, working trans are about $1500.00. I'd go this route before spending 8K with a stealership.

https://www.carparts.com/blog/p0847-code-transmission-fluid-pressure-sensor-switch-b-circuit-low/


The pressure switches/sensors are visible in this video. Notice the dirty trans filter...

https://www.youtube.com/watch?v=nuwNXO_qfhk

 

[pallor]

Update: I had a friend who is skilled with vehicles come over and look at it. We discussed what happened and the dealer. We discussed ordering Switch A and B to change them out - since I had no noticeable mechanical issues. We then drove around in my vehicle - the CEL was still on. The vehicle sounded and performed fine even up hills with acceleration.

He read my code with his OBDII and it was just showing permanement/stored for the p0847. So, he cleared the stored code. We drove around more. No CEL came on.

He suggested I drive my vehicle to work on Monday. I took my vehicle to Valvoline for an oil change (it was time and it wasn't going to the dealer). It was fine there. No CEL. I came home and read the codes with my OBDII and it was not showing any pending codes - just the permanent one. No stored either. I drove it into work fine - about 16 miles each way - took the highway route to get up to speed. No CEL. I drove it home on backroads with significant hills (where the CEL and other lights initially came on - but on a flatter part). I got home and read my codes again and the permanent code has cleared. OBD2 reads green.

I have driven it Monday, Tuesday, and today performing fine. Maybe some debris tripped the sensor due to the extreme cold and the car sitting (and sliding down a hill sideways twice in the ice storm). Maybe something just jostled the connection.

Long story short, its like a Christmas miracle.

Thank you!

PS: I haven't received the transmission fluid test kits yet, but I plan to still submit them.

 

[acidbug]

I would send a sample of the used transmission fluid to Blackstone for testing. If the fluid is dark and burnt smell, this could indicate that the fluid is in bad condition. Also, if the pan was full or low. Glad to hear you were able to swap out The tranny fluid. Ma’am, recommend doing it again at 30,000 miles in this time. Make sure to do a flush. Make sure to use the proper transmission fluid that meets or exceeds OEM fluid from Mazda.

 

[AL Cx5]

Update: I had a friend who is skilled with vehicles come over and look at it. We discussed what happened and the dealer. We discussed ordering Switch A and B to change them out - since I had no noticeable mechanical issues. We then drove around in my vehicle - the CEL was still on. The vehicle sounded and performed fine even up hills with acceleration.

He read my code with his OBDII and it was just showing permanement/stored for the p0847. So, he cleared the stored code. We drove around more. No CEL came on.

He suggested I drive my vehicle to work on Monday. I took my vehicle to Valvoline for an oil change (it was time and it wasn't going to the dealer). It was fine there. No CEL. I came home and read the codes with my OBDII and it was not showing any pending codes - just the permanent one. No stored either. I drove it into work fine - about 16 miles each way - took the highway route to get up to speed. No CEL. I drove it home on backroads with significant hills (where the CEL and other lights initially came on - but on a flatter part). I got home and read my codes again and the permanent code has cleared. OBD2 reads green.

I have driven it Monday, Tuesday, and today performing fine. Maybe some debris tripped the sensor due to the extreme cold and the car sitting (and sliding down a hill sideways twice in the ice storm). Maybe something just jostled the connection.

Long story short, its like a Christmas miracle.

Thank you!

PS: I haven't received the transmission fluid test kits yet, but I plan to still submit them.

Good news!

Cold weather and electronics don't mix sometimes. My pickup threw a weird code the other day I had never seen. It has not been back.

That Stealership would be on my watch list!

Has your trans ever been serviced? It's worth keeping the fluid and FILTER clean.

The trans sample test is a good base line. I'm going to trst an oil and ATF base sample test on our 2024. I'm not using Blackstone any more.

The test will not tell what is in the pan ans how much material is in the filter.

On our Honda, Honda doesn't recommend changing the trans filter! I changed it at 100k. There was a noticeable change in the way the trans shifted. It shifted fine before and crisper after.

In the older Ram Cummins world, we change our ATF every 30k and filter. I also tighten 2 bands on this old school trans at that time. Those that choose to ignore this service have expensive trans repairs. It's not uncommon for these to last over 300k if serviced.

If you plan to keep your CX5 consider changing all the fluids timely. Oil changes are the absolute min.

 

[pallor]

Good news!

Cold weather and electronics don't mix sometimes. My pickup threw a weird code the other day I had never seen. It has not been back.

That Stealership would be on my watch list!

Has your trans ever been serviced? It's worth keeping the fluid and FILTER clean.

The trans sample test is a good base line. I'm going to trst an oil and ATF base sample test on our 2024. I'm not using Blackstone any more.

The test will not tell what is in the pan ans how much material is in the filter.

On our Honda, Honda doesn't recommend changing the trans filter! I changed it at 100k. There was a noticeable change in the way the trans shifted. It shifted fine before and crisper after.

In the older Ram Cummins world, we change our ATF every 30k and filter. I also tighten 2 bands on this old school trans at that time. Those that choose to ignore this service have expensive trans repairs. It's not uncommon for these to last over 300k if serviced.

If you plan to keep your CX5 consider changing all the fluids timely. Oil changes are the absolute min.

I was pretty peeved regarding the dealership. They were going to get a very well kept vehicle for 2500 to sell for probably 15k and force me to pay 40k for a new one that had the same features...

No, my transmission has never been serviced. I think I will get the test kit to just check the fluid integrity. And then I will probably do a drain and refill x 3. I am actually curious about dropping the pan and having it cleaned, but I will need help doing that from my mechanic friends.

 

[pallor]

I would send a sample of the used transmission fluid to Blackstone for testing. If the fluid is dark and burnt smell, this could indicate that the fluid is in bad condition. Also, if the pan was full or low. Glad to hear you were able to swap out The tranny fluid. Ma’am, recommend doing it again at 30,000 miles in this time. Make sure to do a flush. Make sure to use the proper transmission fluid that meets or exceeds OEM fluid from Mazda.

I am planning on sending in the sample.

I didn't change out the transmission fluid - I got a standard synthetic performance oil change. It was time and I wasn't taking it back to the dealership. Valvloline serviced my Mazda MX-3 V6 SE, Mazda Tribute, and Mazda 3 for oil changes as well and I didn't have any issues. I had been taking this CX-5 to the dealership because it was about the same price and I was under warranty until 20k ago. I had taken it out of warranty for oil changes at the dealership but they always wanted me to pay like 1-2k for maintenance services every time I was there. I did have my 100,000 mile service done and ironically, they said I needed to replace the engine head seal gasket (which was NOT on their recommended services list this time) and do a bazillion flushes. But, no actual issues (other than the gasket).

 

[AL Cx5]

I am planning on sending in the sample.

I didn't change out the transmission fluid - I got a standard synthetic performance oil change. It was time and I wasn't taking it back to the dealership. Valvloline serviced my Mazda MX-3 V6 SE, Mazda Tribute, and Mazda 3 for oil changes as well and I didn't have any issues. I had been taking this CX-5 to the dealership because it was about the same price and I was under warranty until 20k ago. I had taken it out of warranty for oil changes at the dealership but they always wanted me to pay like 1-2k for maintenance services every time I was there. I did have my 100,000 mile service done and ironically, they said I needed to replace the engine head seal gasket (which was NOT on their recommended services list this time) and do a bazillion flushes. But, no actual issues (other than the gasket).

Not changing the trans filter after 100K WILL shorten the trans life. Plan and simple.

Modern fluids do not last forever. Read up on what happens to coolant and brake fluid over time and how it shortens the life of expensive components like the radiator and brake master cylinder.

Modern fluids do not last like they did 20 years ago. Brake fluid, DOT 3 and 4 is more hydroscopic than older fluids, DOT 2. Coolant become acidic and eats away the radiator and so forth.

With that said, most folks roll the dice and some get away with it. Others don't and replace their car and complain saying that they changed the oil!

My Tow PIG, 2500 diesel truck, has 265K on it. Trans lasted 230K. If I had kept my foot out of it, that trans would still be going. At 100k intervals I change out coolant, brake fluid. I skipped doing the power steering and just replaced the power steering pump because it was leaking this week. On this old school trans, 2006, it is recommended to change out the trans fluid, FILTER and adjust the bands every 30K. Folks that follow this and don't run tuners, go over 400K on their trans.

On our 09 Accord that the CX 5 replaced, I followed what many Accord guys do and change out the trans fluid with the oil, every 10K. Rather than at Hondas recommended 3 changes at 30K.

Honda doesn't recommend changing the trans filter! I changed it at 100K and noticed smoother shifts. At that time, changed all the fluids, serp belt and replaced the valve cover gasket while adjusting the valves and changing the spark plugs.

I look at doing maintenance like having a small car payment. On the 06, 265K truck, I might $1,000/yr on maintenance and repairs. That is STILL way cheaper than a truck payment. Treated the Honda the same.

Whoever said: "An ounce of prevention is worth a pound of cure" may have been a car guy!

Good Luck

 

[acidbug]

I agree with the above. There is no such thing as lifetime fluid. They’re going under the assumption that most people get rid of their cars by 100,000 so my guess and never mind is that’s considered lifetime. For me considering the way I drive I definitely plan on Doing the transmission and the differential flush around 60,000 miles or so. Even though I don’t tow but I do have a lot foot.

 

[AL Cx5]

I agree with the above. There is no such thing as lifetime fluid. They’re going under the assumption that most people get rid of their cars by 100,000 so my guess and never mind is that’s considered lifetime. For me considering the way I drive I definitely plan on Doing the transmission and the differential flush around 60,000 miles or so. Even though I don’t tow but I do have a lot foot.

X2, I had an 07 Dodge Charger with a lifetime drive train warranty. It was over at a 100k.

60k on those fluids sounds about right. If the brake fluid is 3 years old, I'll flush it at the same time. As a point of reference, on my 2500 truck, they recommend changing the diff fluid between 15 and 30k. Granted these are doing alot more work...

I'll check test the coolant acidity with litmus paper and the % with a refractometer at the 60k mark.