Catalyst Monitor never ready -- but I've done the Drive Cycle

jblc · Nov 3, 2017

Any tips?
The Catalyst Monitor is never ready, despite driving through the recommended Ford Drive Cycles many times, and significant additional mileage.
I'm looking to pass smog.

History: I replaced an O2 sensor, which caused the DTC to clear automatically. There are no trouble codes now. So now I'm trying to get the car set for smog. All other monitors are ready except Catalyst...I can't get it to Ready.

Has anyone encountered this, or have ideas?

RonD · Nov 3, 2017

Which O2 sensor?

The one behind the Catalytic converters, the Downstream O2, is the one that used for "Catalyst Monitor"............but read on

V6 models have 2 Upstream O2 sensors,
4cyl engine 1 Upstream O2 sensor

Both will have 1 Downstream O2 sensor, unless they have Dual exhausts, and Rangers never came with Dual exhausts as far as I know.

Well in fairness Upstream and downstream are both used for the Catalyst Monitor.
Upstream tells computer the Oxygen Level in exhaust at manifolds
Downstream then tells computer there is more oxygen after exhaust has passed thru Cats, so cleaner exhaust Cats are working as they should, and it passes the test

If ALL O2 sensors are not working as they should then Catalyst Monitor test won't start.
This is because test is dependent on all O2 sensors working

Some other things for the test to start
No CEL(check engine light)
Engine fully warmed up
Air temp above freezing << better above but will pass under freezing as well
No exhaust leaks from engine to Downstream O2, if there is an exhaust leak then air gets sucked in, this causes downstream O2 to go low, and stay there, so exhaust is reading "too clean", lol, so test is stopped

Then should only take 10minutes of actual driving, do a few stops and cruise at a few different steady streams between the stops
What test is for is to see if computer is cycling fuel trim Rich then Lean to keep Cats Hot, and that the Cats are staying hot enough to clean exhaust.
This is why the stop and go and steady cruising

jblc · Nov 3, 2017

Interesting notes, thanks. I definitely have done many stops and cruises in the manner you suggested. Engine was fully warm, after driving on the highway for a long while.

I replaced Bank 1, Sensor 1 (p0133). So upstream on passenger side.
FYI it was with this sensor: https://www.amazon.com/gp/product/B000C5UFIK/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Denso lists this as "heated", so though it looks slimmer than OEM it should be correct.

I will check to make sure there are no leaks. Given your note about no leaks, one thing I can think of is perhaps the sensor isn't on tight enough, and there may be a leak. I couldn't fit my torque wrench in there and so used a manual wrench -- I may have not tightened enough.

jblc · Nov 4, 2017

I tightened the O2 sensor to spec, and did some test drives -- but same result.

So it can't be leakage.

Any other thoughts? I appreciate the help

RonD · Nov 4, 2017

If you don't have a "Live data" OBDII reader then get one

Google: Bluetooth OBDII

They are under $20 usually
You do need a smartphone or tablet with Bluetooth and a Free APP, or $5 APP, to see the Live Data while driving

You can then watch ALL the O2 sensor voltage to see if ALL are changing quickly, which is needed for test to start
As said above ALL O2 sensors need to be working or test will not start, not just the one O2

OBDII is a communications standard
It has been required to be used in ALL vehicles sold in North America since 1996 model year
So OBDII reader/scanner, wired or wireless(Bluetooth), will work on ANY 1996 or newer vehicle, required by Law, so not a Ranger thing or even a Ford thing, if it was sold in the US or Canada then it had to be OBD2 compliant
Since it will work on any vehicle, 1996 or newer, it is a good tool to have "in the box"

jblc · Nov 4, 2017

Thanks; I do have a live OBDII reader, which is how I've been getting those codes and readiness monitor data.

All three O2 sensors appear functional. They oscillate between 0.1 and 0.9 V as expected, and change quickly.

RonD · Nov 4, 2017

Air temp sensors needs to be 50-100degF
Coolant temp sensor needs to be above 170degF
So watch the OBDII reader data, those are required for that system test
So even if outside temp is OK the sensor for it might be reading low, same for coolant temp sensor

Also what State are you in?
Different states have different rules for each year vehicle.
Most 2000's or older can have 1 "incomplete test" and still pass

California rules:

Note that a car can pass with some incomplete monitors…a maximum of one on 1999 and earlier cars, and only one (The Evaporative System monitor) on model year 2000 and later gasoline powered automobiles.

All monitors must be complete on 1998-2006 diesel powered vehicles. Any two (2) monitors may be incomplete on 2007 and newer diesels.

jblc · Nov 4, 2017

I'm in California; hmmm, that might be an option to test if with one incomplete monitor!

Okay, I'll check to make sure those criteria are verified. One thing I do know off the top of my head is that coolant temps typically never go above 165, and I'm not sure how to force it higher. Also, outside air is between 50 and 100 F for all the times I've driven it.

At this point, it's been >250 miles since replacing the O2 sensor.

jblc · Nov 5, 2017

Looking back at my previous smog checks, i've always had all 8 monitors ready -- and I haven't changed the coolant system component since then. So i don't think the car got up to 170 F in those cases either.

Anyone else have thoughts on how to set the readiness monitor, or what else to look for?
This is pretty confusing why it's not being set...

RonD · Nov 5, 2017

You may have wrong thermostat in the engine
Since mid 1970s after SAE testing car makers switched to 190-195deg Thermostats from the old standard 180deg units
SAE found 190-195deg coolant temps kept oil cleaner and increased MPG(engine efficiency)
So that low coolant temp will be costing you $$ in fuel if not engine life

Ford temp gauge should be 210deg at 1/2 mark, so you should be running just below 1/2, and then it will go above 1/2 on a long uphill grade or when pulling heavy loads, that would be normal.

Remember cold is the enemy of engine life, faster it gets up to operating temp the better, thats why there are thermostats in the first place, lol.

jblc · Nov 6, 2017

Interesting, i'll check that.

Either way, I was able to complete a few catalyst drive cycles yesterday above 170 F -- it did take a fair bit of work to get there...due to the thermostat? -- but the monitor still did not reset.

All sensors seem operational.

Any other ideas?...

RonD · Nov 6, 2017

No, not really

Catalyst monitor is the last test to run on most vehicles, not just Fords, won't test until all other tests are complete and passed
And it does take its sweet time even after that.

Computers use 1s' and 0's, and there may be a 0 where there should be a 1, showing another test has passed(1) or not passed(0)
So catalyst monitor test will never start, and the 0/1 is not used by anything else so no codes or other issues, just no catalyst monitor test

jblc · Nov 6, 2017

I went through Ford's catalyst-specific drive cycle, though, with all conditions met, and all other monitors are set properly... That procedure is designed to set the catalyst monitor.

Catalyst Monitor never ready -- but I've done the Drive Cycle

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