Cannot get my 2018 GT to smog - NORCAL

[matjam]

Here in ca no O2 sensor can be "not ready" and I am unable to get my car to reset the sensor. I took it to the dealer, and replaced both sensors at the front, and one still doesn't say its ready. So I can't register my car.

I replaced the transmission a while back and cruise still doesn't work.

I'm getting kind of desperate and if anyone has experience getting these cars sorting out the electronics and smog issues please let me know because I'm willing to pay for the time to get it sorted. Dealer tried, a lot, and they couldn't get it to pass. At this point its turning into a giant paperweight in my garage.

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[Palma]

How many miles are on the car? Did the dealer do the transmission swap? I believe smog related issues are under warrantee for 100k by state law or something like that.

 

[bKennedy]

Here is what I found when I Googled your problem. Hope this helps.


Yes, an O2 sensor showing as "not ready" simply means the vehicle's onboard computer hasn't finished its self-tests. It does not necessarily mean the sensor is broken, but it will prevent the car from passing an emissions inspection. [1, 2, 3]

Why does this happen?

• Recent Battery Reset: If your car battery was recently disconnected or replaced, or if diagnostic codes were cleared with a scanner, the computer’s memory resets. This clears all previous test results, setting the monitors to "not ready".
• Incomplete Drive Cycle: The car's computer needs a specific sequence of driving conditions (e.g., cold start, idling, highway cruising) to run the O2 test. If you haven't driven the exact way your car manufacturer requires, the monitor won't trigger as "ready".
• Aging O2 Sensor or Weak Battery: Sometimes older O2 sensor heaters take longer to pass, or a weak battery (even if it starts the car) can cause the computer to suspend self-testing. [1, 2, 3, 4]

Resetting a Ford Mustang battery system involves two distinct processes: resetting the Battery Management System (BMS) to prevent overcharging and electrical issues after a replacement, or performing a hard reset of the vehicle's computer. [1, 2, 3]
Both can be done at home using the straightforward steps below. [1]

Battery Management System (BMS) Reset
If you replace the battery in your Mustang, you must reset the BMS. This tells the car's computer that the battery is new so it adjusts its charging profile accordingly. [1]

1. Sit in the driver's seat and close the door.
2. Press the START / IGNITION button to turn the car to the ON / Accessory mode (do not start the engine).
3. Wait for the dashboard to boot up. Within 10 seconds, complete the following sequence:
   • Pull and release the high beam (brights) stalk 5 times.
   • Press and release the brake pedal 3 times.
4. Watch the instrument cluster: the battery/charging warning indicator will flash 3 times within the next 15 seconds to confirm the reset is successful.
5. Turn the ignition off and open the door. [1, 2, 3, 4]

Hard Reset (ECU/Computer Soft Reset)
To clear out minor electronic bugs, frozen infotainment screens, or erratic sensor readings, you can perform a hard reset by disconnecting the 12-volt battery. [1]

1. Turn the ignition entirely off and wait a few minutes for the electrical systems to power down.
2. Open the hood and locate the battery.
3. Use a 10mm socket wrench to loosen the negative (black) terminal.
4. Disconnect the negative cable and tuck it safely away from the metal post.
5. Leave the car disconnected for 15 to 30 minutes to allow the electrical modules to drain their stored power.
6. Reconnect the negative terminal first (and positive if you removed both) and securely tighten the nut.
7. Start the car and let it idle for 5–10 minutes so the Electronic Control Unit (ECU) can recalibrate and relearn its idle parameters. [1, 2, 3, 4, 5]

How to fix it

1. Drive it: You need to complete your vehicle’s specific "drive cycle." This usually requires driving between 50 to 100 miles of combined city and highway driving.
2. Find your cycle: Exact drive cycle requirements vary by make and model. You can search for your specific vehicle’s drive cycle pattern on OBD Auto Doctor.
3. Do not clear codes: Avoid clearing codes or disconnecting the battery again, as this will reset your progress back to zero. [1, 2, 3]

 

[wingnutt]

this, times eleventy…

1. Drive it: You need to complete your vehicle’s specific "drive cycle." This usually requires driving between 50 to 100 miles of combined city and highway driving.

 

[HoldenSSVandGT350]

this, times eleventy…

This is the way. Same thing happened on my SS Sedan after I replaced the water pump. I had the battery disconnected at same time I did the replacement. Then, within 30 or so miles of driving I went for inspection and got the “not ready” sensor error. Took it out to do the specific GM drive cycles I found on the internet and all was fine and passed with no issues when I took it back for re-inspection. All it needed was about 10-15 mins of highway cruising at 50-70mph to satisfy the “ready” condition.

 

[matjam]

guys, I really appreciate the ... help

but I

a) did google
b) did drive it, like, a lot, and did the full recommended ford emissions reset drive cycle, several times, several permutations (there's several documents out there, all contradictory - I did all of it).

I mean, these are just obvious things to do and its like the same advice from multiple places.

But I think something to do with the tremec swap I did is tripping up the emissions system somehow? I don't know. It will reset all the other emissions things except for just ONE O2 sensor. It used to be in california that you could smog a car with one O2 sensor not ready but they got rid of that.

I've driven it for 500+ miles at this point trying to reset it.

Does anyone have any advice or someone I can take the car to that can get this fixed in norcal that isn't something I can figure out from 3 months of googling and trying all the obvious things.

 

[2015 Silver GT]

Let’s start with this. Is the car stock or has it been tuned?

 

[wingnutt]

I mean, these are just obvious things to do and its like the same advice from multiple places.

yes sir… that’s because we are all shooting in the dark with very little info

Always best to start with the obvious, of which you said nothing in post #1.

Lived and worked in NorCal for almost 20 years, and everyone I know has gotten out of it, smog rules are getting too dicey. only guy I would go to is up in medford, probably too far from Concordia

 

[bKennedy]

I watched an interesting video on testing 02 sensors. This may not be your problem but this is the type of testing you should be getting done by someone that knows what they are doing and with the equipment this guy has.

 

[Gen 6 Mach1]

The Dealer couldn't fix the issue, or you didn't want to pay ? You have 8 years on the emissions warranty,2026 is you 8 th year , you still may be under warranty depending on when your car went into service.

 

[DougS550]

This is the way. Same thing happened on my SS Sedan after I replaced the water pump. I had the battery disconnected at same time I did the replacement. Then, within 30 or so miles of driving I went for inspection and got the “not ready” sensor error. Took it out to do the specific GM drive cycles I found on the internet and all was fine and passed with no issues when I took it back for re-inspection. All it needed was about 10-15 mins of highway cruising at 50-70mph to satisfy the “ready” condition.

Man, I never had that problem on my 19GT. I replaced the battery once and disconnected and reconned the battery numerous times. Good luck. I know this can suck even more since your in California.

 

[matjam]

Let’s start with this. Is the car stock or has it been tuned?

Thank you, the only modification is that I've done the MT-82 -> Tremec swap, with the bowler harness to handle the translation of pulses for the driveshaft.

So nothing that touches anything emissions related, only changes to the ECU to support the change to the tremec.

yes sir… that’s because we are all shooting in the dark with very little info

Always best to start with the obvious, of which you said nothing in post #1.

Lived and worked in NorCal for almost 20 years, and everyone I know has gotten out of it, smog rules are getting too dicey. only guy I would go to is up in medford, probably too far from Concordia

Thank you, I mean, I'm at the "throw money at it to fix it" stage as I'm desperate, at the least I could call them and ask them if they know someone down here, if not I could stick it on a transport.

I watched an interesting video on testing 02 sensors. This may not be your problem but this is the type of testing you should be getting done by someone that knows what they are doing and with the equipment this guy has.

Thank you, this is helpful though I did get the potentially problematic sensors replaced optimistically after doing a ton of drive cycles and the sensors not setting as ready. Note, none of them actually throw a code.

The Dealer couldn't fix the issue, or you didn't want to pay ? You have 8 years on the emissions warranty,2026 is you 8 th year , you still may be under warranty depending on when your car went into service.

Dealer could not fix the issue. I paid to replace the sensors optimistically, they waived the work on it for the most part - just charged me for the parts - they were really good working with me on this. I am not mad at the dealer AT ALL. They've been VERY good to me and went above and beyond as far as I am concerned.

Given there wasn't any trouble codes, there wasn't anything "warrantable" as it were - from all their diagnostics, nothing is "wrong". There's no codes, the parts seemed fine, the sensor just won't "set" as "ready". Hence the "I will throw money at this problem because I'm sick of just bashing my head against the wall".

To be clear, I'm really looking for someone I can pay whatever it takes to get this car working again. I've spent probably 50 hours fucking around trying to get this working myself and my car was 2 weeks at the dealer with them trying to get the sensor to set and at this point its either fix it or a fucking junk it because its not registrable as it won't pass smog. I'm technically minded but I know when I'm out of my depth and this needs someone who actually can get this fixed, not a dilettante. And I've hit my limit of fucking around in my garage.

Thanks guys, I appreciate the time taken to respond. If you're in the area and think you can fix it, I'll happily bring it around and let you fuck around on it and pay you for your time if you actually get it working. Up to a reasonable amount lol.

Bonus if you can get the cruise control working again too, lol.

God, why did I ever replace the transmission, fucking terrible idea modifying cars in any way now with all this emissions bullshit in CA you touch anything at all and it fucking breaks the car.

 

[Gen 6 Mach1]

This may or may not get you around your problem. Here in Az ( maybe Cali too ) if you're insured thru Hagerty your late model Car is not subject to smog certification. If your car is a daily driver , that maybe a factor to them .

 

[jheissjr]

An O2 sensor just outputs voltage equal to the O2 level. It does not have a not ready state. Even in a case of a bad O2 sensor where a malfunctioning sensor output stops toggling voltage on and off, the PCM detects the missing signal and generates a code. If the car is stuck in an open loop, warm up state and the O2 level in the exhaust doesn't transition from a warm up to running level and the PCM is stuck waiting for an O2 signal, maybe that could be a cause. But I think you would have codes if the car is stuck in open loop. Further, the OBD shows the open/close loop status and no guessing is needed. If it is indeed stuck in open loop, being stuck could be good because you can use that for troubleshooting. Another option is the PCM software is in a not ready state for an unknown reason which I think it the more likely case. The PCM does not have a tune and operating OEM correct? The document you are looking for is here - https://www.fordservicecontent.com/ford_content/catalog/motorcraft/OBDSM1802-2018.pdf

 

[mustang_puppy]

I had a similar experience last year when I couldn't smog my car. I'm not sure whether it was my driving to complete a drive cycle for the smog monitors to come back on, or the bottle of cataclean I used to try to help the situation, but either of those 2 solutions worked and I was able to pass smog check, all while having a weak battery which I changed immediately after passing. My car was tuned but has been since flashed back to stock for a different reason.

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