PCM/ECM codes persist - why?

[maestromaestro]

So, I have a few codes that persist even when I ask AccessPort to flush them. I can see the definitions, but the fact that some of them are there is perplexing.
The car runs fine, and there is no engine check light on. Any suggestions as to why these stay on?

These are related to PCM/ECM:

• P060D (Accelerator Pedal Position)
• P2610 (Internal Engine Off Timer)

The above ones are strange - no CEL, no performance issues that I can detect. Is this something that a Cobb tune may throw off? Interwebs suggest that this may have to do with the low battery, but it is not. Also, some suggested a short "somewhere" - which is not useful.

• P2096

This one I suppose has to do with the fact that I no longer have a catalytic converter in the exhaust, and the oxygen sensor is installed in a 'stand-off' in the downpipe to prevent the CEL.

The other two are of the 'U' variety, and my understanding are advisory in nature and can be ignored (but also aren't reset by the AP).

• U0167 (Vehicle Immobilizer issue)
• U0422 (Invalid Data Received From Body Control Module)

The U0422 may mean something different for the FiST rather than this generic description.

Could someone with the knowledge comment please?

 

[Intuit]

PCM/ECM codes persist - why?

It's been messed with.

 

[maestromaestro]

It's been messed with.

OK, I'll bite. Why persisting tho?

 

[Intuit]

Not sure. Do these items have a particular wire harness in common?

 

[maestromaestro]

Not sure. Do these items have a particular wire harness in common?

I have no clue. Doesn't sound like there's any commonality.

 

[Intuit]

Vaguely recall a thread the same pedal code but don't recall what the individual did to resolve.
Can search for individual codes like so...
https://www.google.com/search?q=site:fiestastforum.com+p060d

 

[maestromaestro]

Vaguely recall a thread the same pedal code but don't recall what the individual did to resolve.
Can search for individual codes like so...
https://www.google.com/search?q=site:fiestastforum.com+p060d

That's the first thing I did. Bupkes.

 

[kivnul]

https://www.fiestastforum.com/threads/electronic-gremlins-or-pcm-fail-codes-included.18072/
Someone had a whole bunch of other codes came up, no resolution posted.

https://www.fiestastforum.com/threads/fiesta-st-turned-off-while-driving-and-wouldnt-turn-on.11774/
Very similar codes, had a wire with rubbed off insulation
EDIT: Thread has 2 different posters. Original has no resolution. 2ndary had only 1 similar code but resolved.

 

[maestromaestro]

https://www.fiestastforum.com/threads/electronic-gremlins-or-pcm-fail-codes-included.18072/
Someone had a whole bunch of other codes came up, no resolution posted.

https://www.fiestastforum.com/threads/fiesta-st-turned-off-while-driving-and-wouldnt-turn-on.11774/
Very similar codes, had a wire with rubbed off insulation

Ugh. If that's the case, I will never find it - not about to start chasing harnesses. And, I swapped all the speakers and installed other audio bits, plus the back up camera. So, there are plenty of opportunities for some shit to happen.

I converted to Sync 3, which involved Forscan and a an aftermarket harness. Yeah.

But - immobilizer?

 

[Intuit]

Immobilizer is either the security system or it's that system that government can use the "safely" bring your car to a halt. (yeah, no potential for abuse there)

 

[Intuit]

Ah, here we are...
https://www.fiestast.org/forum/fies...obilizer-malfunction-service-now-message.html

 

[kivnul]

Ugh. If that's the case, I will never find it - not about to start chasing harnesses. And, I swapped all the speakers and installed other audio bits, plus the back up camera. So, there are plenty of opportunities for some shit to happen.

I converted to Sync 3, which involved Forscan and a an aftermarket harness. Yeah.

But - immobilizer?

Story time. I had a 1994 Camry (automatic) that I purchased used. It had an intermittent problem. I would press on the brakes and what would happen is : Reverse light would turn on (Drive light still on as well) and then the car would shake as the transmission would try to shift into reverse. Not great when going 55 down the highway. To mitigate, I would put the transmission in Neutral which is somehow hard coded / hard linked. This would prevent the shaking but the reverse light would still illuminate. The cause? one of the taillight wires running up the trunk support arm was shorting out. If I had something in the trunk that shifted against this wire, I would have the problem. A wire for a taillight caused this. I would not be surprised if a wire running up your dash is shorting giving the computer weird signals.

2nd story time. I took an entry circuit design class (where you design things with AND, OR ect gates with lots of wires and chips) One of the things we would would do is diagram out what you need the circuit to do. Then you simplify it as much as possible. You basically set it up so the chip only understands inputs that you know are possible. Example, you have two signals and only 1 should happen at a time like brake pedal fully pressed and brake pedal fully released. Both can't happen at the same time so your chip is made simple by not caring what happens if both actually do happen. A wire short can tell the computer that two things are happening impossibly at the same time and it can wig out. I am guessing automotive engineers simplify non-critical systems this way to save cost / size of circuits. It is hard, time consuming and expensive to design a system to handle all possible inputs.

 

[maestromaestro]

Story time. I had a 1994 Camry (automatic) that I purchased used. It had an intermittent problem. I would press on the brakes and what would happen is : Reverse light would turn on (Drive light still on as well) and then the car would shake as the transmission would try to shift into reverse. Not great when going 55 down the highway. To mitigate, I would put the transmission in Neutral which is somehow hard coded / hard linked. This would prevent the shaking but the reverse light would still illuminate. The cause? one of the taillight wires running up the trunk support arm was shorting out. If I had something in the trunk that shifted against this wire, I would have the problem. A wire for a taillight caused this. I would not be surprised if a wire running up your dash is shorting giving the computer weird signals.

2nd story time. I took an entry circuit design class (where you design things with AND, OR ect gates with lots of wires and chips) One of the things we would would do is diagram out what you need the circuit to do. Then you simplify it as much as possible. You basically set it up so the chip only understands inputs that you know are possible. Example, you have two signals and only 1 should happen at a time like brake pedal fully pressed and brake pedal fully released. Both can't happen at the same time so your chip is made simple by not caring what happens if both actually do happen. A wire short can tell the computer that two things are happening impossibly at the same time and it can wig out. I am guessing automotive engineers simplify non-critical systems this way to save cost / size of circuits. It is hard, time consuming and expensive to design a system to handle all possible inputs.

It is plausible, of course. In my case, it has to be a HARD short, because all I did was to turn the ignition on, read the codes, attempted to erase the codes and then cycled the start button. The codes that appeared before stayed there - no change. So, either the AP somehow failed to flush them, or they PERSIST.

I think that the inception for me to even bother checking was reading about codes somewhere, which jogged my memory. There are no outward signs of any kind of a problem, at least not that I would notice - and certainly nothing that I could trace to whatever the codes may mean, given the very vague description I could find.