New PCM forced idle

[navybonehead]

OK, so P0191 is a fuel rail pressure code.

Sputtered and died. This says you aren't getting gas!

Quick and easy check. Pull the air intake hose, give it a shot of brake cleaner or starter fluid. If it cranks right up and runs, see if you can keep it alive on the sauce.

Of course, do the regular checks, see if you hear the EFI pump priming for 3 seconds when you turn the key to ON, etc.

Tim

Sure enough, it started briefly while spraying carb cleaner into the TB. But it wouldn’t stay running. It was looking more and more like a fuel delivery issue, but I still suspect it is electronically failing. Live data was continuously showing “open loop due to insufficient engine temperature”.
After sundown it started up and ran great for a test drive.
Strange as it seems, there is a correlation between ambient temp and the engine deciding to start. I live in San Diego where temp has little fluctuations, and it always runs fine when under 70F.

 

[Zorin]

Sorry it took me a bit to get back to this...

"Open Loop due to insufficient engine temperature" only means that the PCM did not enter closed loop control as the engine had not reached what the PCM considers to be fully warmed up. This is not a worry yet.

What IS a concern is a temperature related reluctance to start. THIS may be a by product of your original PCM failure.

At any rate, it sure seems to me at this point, you have nailed most of the problem, and after following along with you, this is what I see...

1. Original PCM did have a concern of some sort, and still does.
2. The replacement PCM also has a concern, but a different concern - either way, it does not work as it should.
3. You also had a wiring concern that you found and solved.

At this point, you can conclude that since the vehicle WILL start and operate on the old PCM, you know at this point that the wiring harness SHOULD be OK - you found the bare wires, and patched them, and regained throttle control, and got rid of the forced idle concern. However, now you have a fueling concern.

What you will need to determine at this point is, does the PCM have control of the fuel pump? Does the fuel pump circuit have a good power and ground? You can see a lot of this on your scan tool by checking live data for the fuel pump circuit. You should be able to see PIDS for the fuel pump such as fuel pump on or off, and you can directly read the data from the fuel rail pressure sensor. Also, you can use Forscan to actuate the fuel pump, and with that, you can see if the fuel pump is activating, if you are getting fuel pressure, and if the pump is bad by activating the fuel pump via the tool and then checking for a power signal at the pump connector.

Tim

 

[navybonehead]

Sorry it took me a bit to get back to this...

"Open Loop due to insufficient engine temperature" only means that the PCM did not enter closed loop control as the engine had not reached what the PCM considers to be fully warmed up. This is not a worry yet.

What IS a concern is a temperature related reluctance to start. THIS may be a by product of your original PCM failure.

At any rate, it sure seems to me at this point, you have nailed most of the problem, and after following along with you, this is what I see...

1. Original PCM did have a concern of some sort, and still does.
2. The replacement PCM also has a concern, but a different concern - either way, it does not work as it should.
3. You also had a wiring concern that you found and solved.

At this point, you can conclude that since the vehicle WILL start and operate on the old PCM, you know at this point that the wiring harness SHOULD be OK - you found the bare wires, and patched them, and regained throttle control, and got rid of the forced idle concern. However, now you have a fueling concern.

What you will need to determine at this point is, does the PCM have control of the fuel pump? Does the fuel pump circuit have a good power and ground? You can see a lot of this on your scan tool by checking live data for the fuel pump circuit. You should be able to see PIDS for the fuel pump such as fuel pump on or off, and you can directly read the data from the fuel rail pressure sensor. Also, you can use Forscan to actuate the fuel pump, and with that, you can see if the fuel pump is activating, if you are getting fuel pressure, and if the pump is bad by activating the fuel pump via the tool and then checking for a power signal at the pump connector.

Tim

Thank you again. Here is an update:
Truck ran fine until yesterday when it would not start in the heat of the day. Wife reported that it didn't idle very smooth at times. Today it was fine again, though I pulled misfire codes this morning.
I finally heard back from the PCM seller, they sent me a troubleshooting flow chart which was all related to throttle control. I put the new PCM back in and relearned the keys, same issue as before (forced idle), so I went back to the original PCM again.
Immediately threw codes P1260, P2100, P2104, P2107, P2110. I may be sending it back.

It looks like this weekend I'll follow your steps to diagnose the fueling issue.

 

[navybonehead]

Thank you again. Here is an update:
Truck ran fine until yesterday when it would not start in the heat of the day. Wife reported that it didn't idle very smooth at times. Today it was fine again, though I pulled misfire codes this morning.
I finally heard back from the PCM seller, they sent me a troubleshooting flow chart which was all related to throttle control. I put the new PCM back in and relearned the keys, same issue as before (forced idle), so I went back to the original PCM again.
Immediately threw codes P1260, P2100, P2104, P2107, P2110. I may be sending it back.

It looks like this weekend I'll follow your steps to diagnose the fueling issue.

Ok so I haven’t had access to Forscan to do all checks on the fuel pump yet. But today I did change the fuel filter. Truck is still about 50/50 on running correctly or forced idle. Always the same P2017 and P2110.
I believe I may still be dealing with a harness issue; when I look at live data, the PCM always sees correct pedal input. However, the throttle position reads a flat line 20% (while in forced low rpm mode). I just can’t figure out if this is a symptom of forced low rpm or the cause of it.

 

[navybonehead]

Ok, I just replaced the TPS harness pigtail. Motorcraft part. Now the truck will only start in forced idle, no throttle control (just like when I used the new pcm). I will test the pcm side of the harness to make sure there’s nothing wrong with my work, but what’s going on here? This is seriously frustrating.

 

[navybonehead]

Ok, I just replaced the TPS harness pigtail. Motorcraft part. Now the truck will only start in forced idle, no throttle control (just like when I used the new pcm). I will test the pcm side of the harness to make sure there’s nothing wrong with my work, but what’s going on here? This is seriously frustrating.

Hi, here is an update on my explorer. I had a local highly recommended shop go through the truck. They deduced that my new PCM was bad and replaced with another remanufactured one. A month later, it died a couple more times on the highway.
So I brought it back last week and they cleaned the battery terminals and replaced the clamps. Same problem. Then they replaced the crank position sensor, same problem. They recommended testing the alternator, it was fine.
Now the shop says they can do a deeper diagnostic, but I’m losing confidence in them to get to the real issue.
Any ideas?

BTW, when it dies on the road, it always shows a wrench light for 5-10 seconds before dying, and always restarts and runs fine once it has been put in park.

 

[Bazz270]

Looks like they have zero idea about car diagnostics

Try to retrieve the recorded DTCs for the beginning

 

[navybonehead]

So here’s an update. The truck still dies, almost exclusively when it is hot out and when driving over 60mph (slower with a load). The shop has a new computer to install, but they want to charge me for parts so I have not agreed to do this again. I replaced the fuel pump with no change to the issue. Same codes always come up- vehicle block ID mismatch, ECM error, throttle control codes, and forced idle or forced engine shutdown.

 

[Bazz270]

Havent you try to go thru the factory pinpoint procedures per each code?

 

[buumaster]

So here’s an update. The truck still dies, almost exclusively when it is hot out and when driving over 60mph (slower with a load). The shop has a new computer to install, but they want to charge me for parts so I have not agreed to do this again. I replaced the fuel pump with no change to the issue. Same codes always come up- vehicle block ID mismatch, ECM error, throttle control codes, and forced idle or forced engine shutdown.

you replaced new throttle body?
you checked wiring from TAC and TPS all the way to the PCM?
you replaced new PCM?
And your Explorer still randomly gives you yellow wrench with the fault codes of throttle body and goes in to limp mode untill you reset your PCM?

You also replaced TPS connector but in what condition is your TAC connector?

 

[Ruddy]

I feel your pain!
Mailed mine to Neatauto and they said there was nothing to fix.
Flagship 1 pulled 3 PCM's off the shelf and could get any to pass their tests.
Now on 2nd CarComputerExchange PCM since they forgot to change VIN on the first one. It ran ok for a while then went batshit crazy. Forscan analysis points to PCM. The 3 main things going nuts are all on fuse 42, so could be wiring, but like you swapping PCM's back and forth why didn't that happen on old PCM? And old PCM's problem has been fine.

 

[navybonehead]

you replaced new throttle body?
you checked wiring from TAC and TPS all the way to the PCM?
you replaced new PCM?
And your Explorer still randomly gives you yellow wrench with the fault codes of throttle body and goes in to limp mode untill you reset your PCM?

You also replaced TPS connector but in what condition is your TAC connector?

I’ve replaced both of the throttle pigtails.
The thing almost always fires right up once I get it into park without a PCM reset.
The shop wants to put in another used PCM, but they want to charge me for parts even though its only been a couple months since they put it in.
Is there anything other than PCM as a culprit? To answer above, I haven’t found the pinpoint procedures, does anyone have a link?

 

[Bazz270]

Any ebay digital or hard copy will be ok

I dont think there is a free link anywhere

 

[ggomez2]

I’ve replaced both of the throttle pigtails.
The thing almost always fires right up once I get it into park without a PCM reset.
The shop wants to put in another used PCM, but they want to charge me for parts even though its only been a couple months since they put it in.
Is there anything other than PCM as a culprit? To answer above, I haven’t found the pinpoint procedures, does anyone have a link?

Did you ever solve your issue with the forced idle? My 07 EB V8 is doing the exact same thing.