attar84

I searched for a solution here for days, no luck. Please help me.

2008
120K miles
No engine mods
I do not track the car

engine light is on, scanned and got these codes:

P0118 Engine coolant temp sensor 1 circuit high
P2184 Engine coolant temp sensor 2 circuit low
P2185 Engine coolant temp sensor 2 circuit high
P0420 Catalyst system efficiency below threshold bank 1

the P0420 has been on for a while before the other 3 codes, don't think they're related. My catalytic converter and o2 sensors were damaged, i replaced them both but that code will just not go away. I know i installed everything right, not my first time. I tried unplugging the battery for like an hour, code went away for a few days but came back on.

The other 3 codes (ECT sensors): Recently, the cooling fan stopped working, replaced it, flushed the radiator and put new coolant and everything is fine. Two months later, these 3 codes pop up. The heater inside the car takes forever to come on, and only comes on while driving, and gets cold when idle. My first question is, apparently 2006+ models have two sensors instead of 1; where are they located? Pictures would be very helpful. Second question, is it possible that only ONE sensor is bad and it's feeding the other sensor with bad data, hence the code? How would I know? Or should I just replace both?

Thank you in advance! I just want my baby healthy and ready for inspection (which is 2 months overdue)

****UPDATE: I checked both sensors and their harnesses with a multimeter, all working fine. I flushed and bled the coolant system (using both valves) and now the heater seems to be working fine, I'm guessing air was trapped. However, the codes remain. This coming weekend, I will take the CAT and O2 sensors out and re-install, maybe I messed up somewhere so hopefully I can get rid of the P0420.

I still need help with ECT codes...someone has got to have an answer...

attar84

No body?

Slowcrash_101

Did you bleed the air out of the coolant the right way? Is your secondary o2 missing it's head? Sometimes when the cat gets damaged it'll take out the secondary o2 sensor. It'll still be threaded in there except it'll be decapitated.

attar84

I followed Billman250's coolant bleed thread; I'm pretty sure there is no more air trapped in the system.

As far as the o2 sensor, I replaced that as well with the cat.

Midnightdennis

A defouler would fix the P0420 code.

attar84

Even though it's a stock cat? I really want to fix whatever the issue is rather than hide it.

Thanks

jts09

Since the heater stops working at low rpm (idle), it's possible that your thermostat is bad. Thermostats are built to fail in the full open position to allow coolant to flow to prevent engine damage. This also won't allow the engine to maintain its proper operating temperature. I had a thermostat fail in the dead of winter and I would get no heat at all. Made for some uncomfortable driving until it was replaced.

attar84

The heater works fine now after I bled the coolant. The car doesn't overheat and temperature gauge seems to be functioning right.

A friend of mine and I checked everything again yesterday and all symptoms lead back to the ECT sensor. When I tested the sensor for resistance, it was behaving normally (less resistance when hot and vice versa). However, I don't know what resistance numbers I should be getting with different temperatures, looked everywhere too. So I just went ahead and replaced the darn thing ($25). The CEL codes did not go away..my friend suggested 'clearing the codes' using my obd scanner. So now I'm just waiting for the ecu to relearn everything and hoping them codes don't come back. I"ll report back here in a few days.

Thanks everyone.

attar84

Update**

After a few days of driving, the only code that came back was the P0420..So changing the ECT sensor seemed to have fixed the other 3 codes. I've yet to get under the car to examine the CAT and O2 sensor.

P1'05/P2'03 pilot driver

P0118 Engine coolant temp sensor 1 circuit high
P2184 Engine coolant temp sensor 2 circuit low
P2185 Engine coolant temp sensor 2 circuit high
P0420 Catalyst system efficiency below threshold bank 1

I had these codes on an '05 pilot with ~245k miles, but also including p0117, p0113, and p0112, all relevant to ECT or IAT sensor voltage or input being high or low. I have had the p0420 code off and on over the last 1.5 years, but it vanishes with no intervention (thankfully in time for the last inspection). Similarly, I recently replaced the radiator fan and thermostat following an overheating issue, but this was done in the summer (about 2 months prior to these codes) so cabin heater function was not assessed. A/C usage seemed to burden the engine more than normal, which I forgot to assess upon fix, but the engine definitely started and idled much more smoothly after fix...

Both ECTs and the IAT were sensitive to heat/cold in a multimeter check. At ~65F they read 2.6-2.8 ohm before the hair dryer (sorry didn't record exact numbers). The ECTs were clean (coolant only) but the IAT was mostly coated with a dark and stubborn residue, which minimally cleaned off with kerosene to expose one side of the tip; maybe carb cleaner would work better, but not clear on what either of these will/would do to the material. The IAT was similarly sensitive to heat/cold as before the incomplete cleaning, but maybe I'll replace it anyway...

I added di-electric gel to the female ends/plugs, cleaned out 2-3 very small chunks of debris (did not replace the cat), and the engine light was gone upon cranking, zero driving required, including the p0420.

Hope this helps someone in the future. I am by no means expert, and my issue probably different from attar84, but particularly on aged vehicles a basic cleaning (and perhaps the di-electric) may be a good starting place for these codes.