RKRL

Thank you so much for viewing this thread, hopefully you can throw in some of your advice in helping me solve this problem.

I'm getting a P2185 code along with a P0118 and a P0155 code. I'm also getting a "Check SH-AWD" light, but I've come to find out that that light goes away when the ECT code is resolved. I believe I read up that
Acura designed it to be this way - when the Check Emissions/Check Engine light comes on, the SH-AWD is automatically disabled.

What else I've realized is that the P0155 and P0118 code go away when the ECT code is resolved. I bought a new temperature sensor from Autozone, replaced it with the old one (car is a 2011 and only has 50k miles on it?), turned the car on, and the check engine light went away, along with all the other codes.

I had the car running for about 5 minutes, then shut it off, commended myself on a job well-done, a few minutes later, turned the car back on, and to my desperation, the above codes came back on. P0155, P0118, P2185 and Check SH-AWD.

I was checking fuses - they all appeared to be fine, with the exception of the 30AMP fuse for the COND fan - that was bad, so I replaced it (vehicle previously had been hit in the fan area, likely causing the fuse to go bad).

SYMPTOMS/EVALUATIONS
- Both fans work, I checked by turning the A/C on.
- The coolant level appears to be good.
- I even tried to bleed the system, using a special funnel, and it appears to have been bled (no more bubbles).
- Car does not overheat, temp stays steady in the middle, I ran the car for 5-10 minutes at a time, and then took it out on the road for a quick run around the block - still no overheating, temp rose to around halfway and stayed there.
- Cooling fan does not appear to come on, nor did not appear to come on at any point in time, other than when I turned the A/C on.
- Engine does not appear to stall or jitter or run poorly.
- Coolant isn't OEM from the dealer, but it is clean and isn't rusty or dirty - as some online diagnosis pages advised of.
- Using a scan tool (not the best one, but gave enough info), I kept an eye on the coolant temperature readings and the two numbers I remember seeing (after on and off cycling), were 163F and 173F. I kept the car running for a few more minutes, revving it a little, to try to get it past 190F (which I believe is when the fans come on), but it doesn't appear to have reached that temp - maybe my scanner doesn't get live readings? Only readings at start-up?

Do note that I did have the water pump go bad, and that the car had sat without coolant for maybe a month or so. Maybe a stuck thermostat?

I know this is a lot of information, and maybe you're not a certified mechanic or cooling expert, and that's okay. But based off of the symptoms I'm having, and your general knowledge (or in-depth knowledge) on how a car runs, how the cooling works, etc. what does this appear to point to?
Maybe I'm slowly peeling away at the answer by typing this all out, but maybe the ECT is not receiving hot coolant because the thermostat is not opening up? I'm guessing most of the hottest coolant is in the engine itself, and all of it is held back by the thermostat. When that temperature increases to a certain point, it opens the thermostat, and hot coolant flows right past the temperature sensor, giving the 190F reading, throwing the fans on. Or maybe the thermostat is stuck open?

Any advice would be helpful!

Thank you

csmeance

Did you leave the rad cap off, heat on full blast to bleed the system of air? If not, that's what you have to do! It could be pockets of air causing the issue.

It could also be a bad sensor from sitting without coolant or tons of other things so lets work step by step. The cooling system has a LOW and HI speed fan setting, HI should come on when the coolant gets to about 204-206F

RKRL

I used the special funnel with the attachment inserted into the coolant cap area, and had the car running for 5-10 minutes; I saw some bubbles come up, but shut the car down after there was no bubbles after a few minutes. Should I have it running for a longer period of time to bleed it? I am re-using the original ECT sensor located on the bottom of the radiator itself, but bought a replacement one that goes on top where the upper radiator hose goes into the engine. I guess there's two total sensors for the coolant temp. I can try bleeding the system again, for a longer period of time, and then maybe from there, if the issue isn't resolved, I'll try to check the voltage going through the wiring at the connector plug-in. This should eliminate a poor wiring issue. What are your thoughts on the thermostat being the issue? Online search suggested a P2185 can be caused by a stuck or leaking thermostat. Is it possible that the car sitting without coolant through some cold weeks may have seized the thermostat? So maybe it's stuck open and the coolant isn't getting the proper temperature reading because of the constant flow? So maybe it's throwing that code?

Thank you for your response by the way, I do appreciate it!

csmeance

After you saw the bubbles come up, did you add more coolant? The radiator needs to be filled to the top and the air needs to be 100% out of the system. If there's air you will get faulty readings from the sensor. Yes there is an upper and lower sensor!

RDX022355

Any updates on the repair?

I recently had to replace the radiator. The OEM Denso radiator ordered from Acura came with a new coolant temp sensor. I reconnected the sensor harness, refilled with Honda Type2 coolant, ran the engine without the cap on the radiator, added additional coolant to top it off, waited to see if the air bubbles are gone, added more coolant. When the rad was filled to the top and there were no bubbles I put the cap on the radiator...

I still have P2185, that is the only code I can detect with a cheapo ELM 327 Bluetooth scan tool. Additionally, there is no indication of the engine temperature on the dashboard, it seems to be completely OFF, i.e. I would expect some indication similar to the fuel level gauge on the dashboard. I also did not observe the fans running, which might be related to faulty sensor circuit as there is no signal to ECU to turn them ON...

Any advice on what else needs to be done? Should I be trying to replace the thermostat? How would I check if it is a T-stat related issue.

I

acuratech481

The two sensors are for determining a stuck thermostat. If ECT Sensor 2 never comes close to the temperature of ECT Sensor 1 then you have a stuck thermostat.

RDX022355

The good new I can see temp reading from both sensors on the OBD scan. As the engine warms up, temp readings are getting close to within 10deg. I also see on the dash that engine is within normal operating temperature. Thus, I conclude that both sensors are alive and t-stat is working!!!

On the other hand, P2185 does not disappear even when I try to erase it using reset function of the OBD scanner. Any further advice on what else to check?
Thanks.

acuratech481

DTC P2185:

ECT Sensor 2 Circuit High Voltage
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.

Is about －40 °F (－40 °C) or less, or 4.92 V or more indicated?

YES —

Go to step 3.
NO —

Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at ECT sensor 2 and the PCM.■

1. Turn the ignition switch to ON (II).
   
2. Check ECT SENSOR 2 in the DATA LIST with the HDS.
   
   
   

1. Turn the ignition switch to LOCK (0).
   

1. Disconnect the ECT sensor 2 2P connector.
   

Is about －40 °F (－40 °C) or less, or 4.92 V or more indicated?

YES —

Go to step 8.
NO —

Go to step 20.

1. Connect ECT sensor 2 2P connector terminals No. 1 and No. 2 with a jumper wire.
   
2. Turn the ignition switch to ON (II).
   
3. Check ECT SENSOR 2 in the DATA LIST with the HDS.
   
   
   

1. Turn the ignition switch to LOCK (0).
   

1. Remove the jumper wire from the ECT sensor 2 2P connector.
   

1. Turn the ignition switch to ON (II).
   

Is there about 5 V?

YES —

Go to step 12.
NO —

Go to step 16.

1. Measure the voltage between ECT sensor 2 2P connector terminal No. 1 and body ground.
   
   
   

1. Turn the ignition switch to LOCK (0).
   

1. Jump the SCS line with the HDS.
   

1. Disconnect PCM connector A (49P).
   

Is there continuity?

YES —

Go to step 27.
NO —

Repair an open in the wire between the PCM (A27) and ECT sensor 2, then go to step 22.

1. Check for continuity between PCM connector terminal A27 and ECT sensor 2 2P connector terminal No. 2.
   
   
   

1. Turn the ignition switch to LOCK (0).
   

1. Jump the SCS line with the HDS.
   

1. Disconnect PCM connector A (49P).
   

Is there continuity?

YES —

Go to step 27.
NO —

Repair an open in the wire between the PCM (A21) and ECT sensor 2, then go to step 22.

1. Check for continuity between PCM connector terminal A21 and ECT sensor 2 2P connector terminal No. 1.
   
   
   

Is DTC P2185 indicated?

YES —

Check for poor connections or loose terminals at ECT sensor 2 and the PCM, then go to step 1.
NO —

Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.■

1. Turn the ignition switch to LOCK (0).
   
2. Replace ECT sensor 2.
   
3. Reconnect all connectors.
   
4. Turn the ignition switch to ON (II).
   
5. Reset the PCM with the HDS.
   
6. Do the PCM idle learn procedure.
   
7. Check for Pending or Confirmed DTCs with the HDS.
   
   
   

Is DTC P2185 indicated?

YES —

Check for poor connections or loose terminals at ECT sensor 2 and the PCM. If the PCM was updated, substitute a known-good PCM, then recheck. If the PCM was substituted, go to step 1.
NO —

If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.■

1. Reconnect all connectors.
   
2. Update the PCM if it does not have the latest software, or substitute a known-good PCM.
   
3. Check for Pending or Confirmed DTCs with the HDS.
   

RDX022355

Thank you, Sir. This is awesome guide!

RKRL

UPDATE to those of you still checking out this thread/forum. I did some testing with a multimeter. The PCM is supposed to give off around 5V to each Coolant Sensor (there are two on the 2011 MDX). I checked, and I'm getting 5.1V and 5.2V to each sensor, so the PCM must be sending out a good signal (5.1V and 5.2V is actually too much, it should not be greater than 4.92V). I tested the resistance on the sensors as well, and was getting good readings. The P0155 code was the culprit. This is the code for the oxygen sensor up front. After a little bit of communication with an experienced Acura tech that I found through this forum, I decided to run some tests on that O2 sensor, and turns out there is no resistance in it. Took it out with a borrowed tool from Advanced Auto Parts, and it had visual damaged to it. Bought a new sensor from O'Reilly Auto Parts, and ALL codes went away. I was initially thinking maybe the coolant sensor issue was causing the oxygen sensor code (since they're on a similar circuit/work together), but turns out it was the other way around. I believe that the broken O2 sensor was causing extra voltage to go to the coolant sensors, throwing all the codes.

thoiboi

what brand O2 sensor did you buy? If it's not a Denso/NTK/ OEM equivalent, expect to replace it again sometime soon. hoping it's not a Bosch

RKRL

It was NTK. I initially thought that Denso was the original, but when I removed the old one from my vehicle, it had NTK stamped on it, and the NTK was actually cheaper than the Denso by around $20.

thoiboi

acuratech481

Glad I could help!