gqdabien

I was looking for blown fuses and might have pulled the ECU fuse a month ago.

Since then, I tried to smog my car recently. However I failed the sensor test since my Catalytic sensor kept coming up Not Ready on the OBD2. The only thing i was told was drive it more.

Since then I have put about 400-500 miles on my car, and with my own OBD2 reader the cat still says "Not Ready". I have read online that there are specific drive conditions that must be met in order to pass the cat sensor.

I've tried cold starting the car and letting it idle for 5 minutes.
Drive 60mph for several miles
Drive in city traffic

Does anyone have any suggestions?

gqdabien

Took a long drive up and down PCH today going about 45mph for about 30 miles, took it on the fwy going 60-65 mph for another 30 miles. still cat not ready sensor.

Anybody got ideas?

bbsciontc

Can't say for sure but here are my thoughts:

Is the catalyst the only thing that is not showing as ready? What about the other sensors? If it's just the catalyst, that suggests the secondary O2 sensor, wiring or the converter itself. If it's more than that, then there's either an issue with the constant power source for the ECM or the a problem with the ECM itself.

gjpjr84

how old is your battery? have you replaced it recently?

I had this issue with mine for a while. the had to do their drive cycle thing specific to get it to pass, it was a whole nightmare that took a while to figure out.
the constant power issue bbsciontc mentioned may be the problem, after I replaced the battery, I have not had the issue again.

there were no other issues or test showing that the battery was actually bad or anything, I just decided to replace the battery.

gqdabien

Thanks so much guys for the responses.

@bbsciontc
Something strange just happened, i checked the obd2 scanner and now EVAP & CAT both show "not ready". Is this indicative of the ECM not getting proper power? And could I be experiencing this even though engine and other cabin electronics/amp/sub start up fine?

@gjpjr84
The battery has been on the car since at least 2010 (possibly earlier). Were you able to pass the sensor after doing the specific drive cycle before replacing the battery? Or only after replacing the battery did it become ready?

sorry for all the questions, i just want to avoid spending unnecessary money.

gqdabien

So i went ahead and got the battery checked out @ O Reilly and they said the battery was still good. It has quarter life still but the voltage is still at 12v.

bbsciontc

Here is a diagram of the ECM harness and pinouts. This is assuming you have a 2005-06. The newer ECMs are different and I don't have the diagram.

It may be possible that even though an ECM isn't getting constant battery power, it may be able to function once the ignition is turned, especially since the main power source for the ECM is switched with the key cylinder.

With the ignition off, check that the "Always on" terminals are receiving battery voltage, a minimum of 9V, although you should definitely be higher than that. It's the first two indicated in the diagram. If that's good, then the ECM is getting voltage needed to retain memory. If not, there may be a fusable link that has busted for some odd reason.

Beyond that, you will have to troubleshoot on a step by step basis, starting with the secondary O2 sensor which is monitoring the catalyst. Unfortunately it's a process of elimination exercise. Not the most fun.

gqdabien

Thanks for the great PDF! Before I unplug any cabling to check for voltage. Would it be safe to think that the ECM fuse in fuse box is doing OK since all the other sensors are keeping a "Ready" state. I kind of have a urge to check the ECM fuse, but not if unplugging it could lead to wiping out its memory.

Would unplugging to check for voltage on the harness lead to wiping out its memory? I just want to make sure I don't undo any of my previous driving miles if driving it more really is the culprit.

Thanks again!

gjpjr84

the dealership was eventually able to get it to show as ready by following a specific routine that I do not know the details of, and they just used the same routine whenever it needed inspection again.

their possible diagnosis was the same, of it not having constant power somehow, but as I said before, there was nothing wrong with my battery or wiring that they or I could find.

I had the issue until i decided to change my battery, I haven't had the problem again.

bbsciontc

OBD2 is a strange animal. It has a series of things that it looks for to set readiness. Almost a checklist. What that means is that in some cases if a particular sensor is not setting as "ready" it may not proceed to set readiness on subsequent sensors. It depends which ones however. It is possible that the evap may being hanging up just because the catalyst isn't setting as ready.

If you pull the fuse, harness or battery, yes, you many reset the computer. I will tell you this though, I've been pulling mine almost every week trying to diagnose an issue I am having with an aftermarket computer. Each time I reset the ECU, all the readiness codes were set to ready in less than 100 miles and maybe 4 or 5 driving cycles. If all is working well, it really shouldn't take long. If its accessible enough and you have narrow probes on a multimeter, you should be able to test for voltage without unplugging the harnesses from the ECU (probe from the wire side of the harness)

Some people have different experiences with this, and it may be a function of the type of driving you need to do for each test. I do a good bit of highway, but a portion in bumper to bumper traffic so that would be considered city driving. Also, sometimes you need about a half full tank for the evap test to set. It will postpone the test if the tank is full or nearly empty.

gqdabien

Update! Before i got a chance to check the voltage to the ECU, I decided to take the car on a canyon drive near my house, round trip about 40 miles and cruise controlled it @ 50-52mph the whole way.

CAT sensor "READY" !! :D

Now onto the EVAP...

bbsciontc

Good stuff! The evap should set on it's own now. Generally, the tank needs to be about 30-70% full, and sit overnight for about 8 hours or so. What happens is that after the car is fully cooled off, a pump turns on an pulls vacuum in the evaporative emissions system. It then verifies that the system can maintain vacuum (i.e. no leaks) and if all is well, it should set to ready. Give it a night or two and you should be set.

gqdabien

Having trouble getting the EVAP to set to ready. Been driving it the last few days with 10-12 hr cool-off periods. Also filled the gas twice only up to 3/4 full. Anybody have drive cycle suggestions?

I tried following this one i found online:
Toyota/Lexus OBD-II Drive Cycles | Car OBD Diagnostics, ECU Chip Tuning & Auto Repair Support

On step 5. I did let the car sit about 10 min on idle before turning it off, 50 minutes seems a bit extreme doesn't it?

bbsciontc

Here's a better reference specific to this engine. All conditions must be met for the test to begin.

Also, check if there are any pending codes (do not reset or you will have to set the catalyst again). It is very common for these cars to have a gas cap leak, causing you to actually fail the evap test (small and/or gross leak detected). I changed my cap twice with oem, and none fit very well. An aftermarket replacement (Stant) cap fit much better and made my codes go away.

gqdabien

Thanks for the much more detailed instructions. Is it possible that i'm not meeting these conditions when i let it sit overnight in garage or driveway in SoCal? Everything else I'm pretty sure i'm meeting the requirements (also no codes on my reader).

- The engine coolant temperature is between
4.4°C and 35°C (40°F and 95°F).
– The intake air temperature is between 4.4°C and
35°C (40°F and 95°F).

tCb00b

iTrader: (1)

Is there a check engine light on in the instrument cluster? What codes are you getting when running diagnostics? How many miles are on the car?

gqdabien

No check engine light, no codes thrown on obd2 reader. I have about 94k on the car now.

tCb00b

iTrader: (1)

Interesting. Around that mileage I started getting evap codes. I recently replaced my gas cap gasket and downstream o2 sensor but I was getting codes for both. It sounds like the ECU is resetting before it can complete a drive cycle.

gqdabien

Checked this morning. All I/M monitors ready! I guess all it needed was an extra couple days of sitting overnight to set.

Going to get Smog tested today! Thanks everyone.