I'm getting a persistent P0237 code, would appreciate assistance in troubleshooting.

Symptoms: P0237 code . 2001 Excursion PSD. No noticeable change in start-up, running, driving, fuel economy, anything. Always happens with key on before starting, sometimes it'll happen during cranking. Truck always starts.

Turn k​​​​ey on, SES light pops up. Without starting engine, go into the diagnostics on the Edge, Contoroller (on stock tune) check codes, P1000 and P0237 (I know that P1000 is b/c codes were cleared.) Clear codes, cycle the key, and P0237 comes back on. Without resetting the codes, start the engine (starts fine), SES still on. Check codes, P1000 and P0237 still there. Clear codes, SES light goes off, and for the duration of using the truck, right until I turn off the key, the SES light never comes back on and P0237 never re-appears.

But shut off the truck and do it again, and the cycle may begins anew -- but not always. Sometimes I can start the truck and the light does not come on, 50/50 chance.

Troubleshooting to date:

I checked the voltage and resistance as recommended, all checks correct:

I have 5.05V reference to the harness on the brown/white wire.
I have almost no resistance to the battery terminal on the gray/red wire
I am seeing 1.5V from the center light green/black wire with the sensor plugged in, key on engine off.
I have no way to test continuity to the PCM, however I did watch the MAP (abs) value/PID on the Edge Controller change as I blew into and sucked on a hose attached to the MAP sensor nipple. It's showing only whole numbers and indicates "14" with Key key on engine off, indicating the PCM is seeing the MAP sensor.

I replaced the MAP sensor with a NAPA part. No change in behavior.

Cleaned all MAP contacts and used dielectric grease. PCM contacts are in good shape since I pulled it in December to install a DP Tuner chip and used dieletric grease. Behavior does not change with chip removed.

And yet, I still have a code P0237.

Thought maybe it's being caused by low voltage, so I left the truck on a battery charger all night before leaving for a long trip...and the P0237 code did not pop up when I turned the key on. Truck started fine (7 degrees outside but it was plugged in overnight this time) and the trip was uneventful.

I also realized that I did not get the code on startup the day before when the truck was very hot - I made a quick trip into the bank - leading me to believe that this code is related to voltage drop when the glow plugs are engaged.

Installed new batteries, starts fine, I clear the code with the Edge and it runs fine. Averaged 10.5 mpg round trip from NJ to TX pulling 15k pound trailer. SES popped on quite a few times during the trip.

I'm now daily-driving it and...50% of the time I'm getting a P0237 code on key on, before starting. But the truck still runs fine and clearing the code with the Edge makes it go away for the duration of the trip.

I'm stumped. I want this fixed, especially before the next OBD2 emissions check comes up.

 

Yes, I'm scratching my head on this one too.

Going to throw my thinking up here, I don't think I am really getting closer to the resolution as much as I am posting stuff that other clearer thinkers can pick apart... I feel like I am finally getting closer to understanding how the engine controls work.

I would first think it was a boost leak. Thinking low boost due to a leak could trip the code for the sensor. But no way it could be that since the engine is not running yet. So the sensor? Well, how could there be a low boost reading when there is no boost? So I am ruling out the sensor.

You replaced the MAP sensor with a NAPA part. Having trouble seeing how it could be that. And you had no change, so fine. Did you keep the original part? JIC, as it is an OEM sensor and is probably good.

So I'm thinking about the 5V reference signal. Can't be the alternator, since the engine codes before start. Battery grounds? Check both batteries. Ground from engine to frame. Ground for the electronics... And the same for battery 12V. If both batteries are not properly connected, then the glow plugs could be sucking voltage too low. Though I think this would lead to a no-start before getting this code... And you can start the truck... Chasing my tail here...

Hmm, the reference also goes to the IPR IIRC. Pull the connector and check for oil and dirt?

 

That's what I'm looking for: a different perspective, something that I missed. I've been playing with this for months so I need another viewpoint.

Checking battery grounds and and terminals, and checking resistance between the two of them is a good move, I'll do that. It makes sense, since I'm leaning toward the problem potentially (sorry) being a reference voltage drop when the glow plugs are on. Another good check is the reference voltage drop when the truck is cold and the glow plugs are on; I did not do that.

I'll pay a lot more attention going forward, as I seem to feel like it happens much less when the truck is hot (if at all) than during a cold start. Note I wrote "I left the truck on a battery charger all night before leaving for a long trip...and the P0237 code did not pop up when I turned the key on. Truck started fine (7 degrees outside but it was plugged in overnight this time) and the trip was uneventful." To clarify "plugged in overnight" meant the block heater was plugged in. I wonder if the glow plugs even came on...?

I have checked voltage and connections at the IPR, I do recall pulling and cleaning it and putting some dieletric grease in there. I'll check it again.

I'm also going to twist myself in there and remove and reinstall the PCM. This problem seemed to start right about the time I removed it to clean the board for the DP Tuner chip. The harness is snug, everything works, but it doesn't hurt to check it again.

Did not reinstall the old MAP, but as you noted I saw no difference in behavior with the NAPA part.

Keep the ideas flowing!

 

I'm sure I can look it up, but maybe if you put in the description of what P0237 is in your first post, that would get more input.

Edit: found it
P0237 Turbo Boost Sensor A Circuit Low Input

I just battled an electrical issue myself and while I'm not sure mine was with the PCM, I did remove it and test continuity on the relevant pins for my issue. When reinstalling the PCM, I left the harness loose and secure the PCM to the bracket. After that was in place & tight, I then lined up the harness plug and gently slid it in to position, then tightened it all down. I did not use any dielectric grease, but next time I will but only in the areas to seal the case to harness.

 

Possibly the wiring is shorting to ground somewhere since it is intermittent and also happens when the truck is not running?

 

Well, here's a new one: it did it in the middle of the drive home from work just now. System voltage was 13.9-14.1, and absolute manifold pressure did not spike or drop that I could see. It did pop the code on startup cold, and I had cleared it.

So now I'm less suspicious that it's battery voltage-related.

Good info. This did seem to start right when I removed and installed the PCM, so while it seems superstitious your procedure is worth a shot.

 

Just a note on the dielectric grease. It is actually an insulator, so be careful not to slather it all over the connections / contacts. They are usually tight enough that a clean contact is made, but if you have luck like I do you could have found one that is not. Also if this started about the time you installed the chip there may still be some "stuff" on the contacts.

 

Today's troubleshooting process... (TL;DR: it's fixed...maybe).

Turned on key to verify issue was still there; it was. All dash lights came on as the key-on check, SES went out, counted to 5, SES came back on. P0237.

Ok, figured I'd pull the PCM and check the wiring. It's a nice warm day today, unlike the fingertip-freezing weather I did it in last time, so with a generous combination of extensions and swivels I got the PCM disconnected, then out. I looked at all the pins in the PCM, all was well: nothing bent or pushed in, no visual corrosion, no obvious excess of dieletric. Visual inspection of the wiring harness inside looked good as well: female pins all there, nothing bent, nothing pushed in, no obvious corrosion or excess of diaeletric.

With help from my beautiful wife, some paper clips, and a Fluke, we verified connectivity of all three wires from the MAP sensor plug to PCM harness pins 79, 90, and 91. All good.

So, with @papadelogan's post #4 in mind, I installed and secured the PCM in place, made sure all was well. Then I went into the engine compartment and carefully lined up the harness plug, started the bolt by hand with a short socket and tightened as well as I could, then used my generous combination of extensions and swivels to snug it down. Re-connected batteries and jumped inside.

Key on, all lights light up. a second later, all lights go off. Count to 5 and...SES back on! P0237 and another code, something like P0600! DAMMIT.

Oh, wait a sec, did I remember to reconnect the MAP sensor? <walks around front of truck> Nope, I did not. Dee-dah-dee. Plug in MAP sensor, back inside, key on sequence, count to 5 and...no SES! Truck starts, runs, wait 30 seconds, no SES! Key off, key sequence again, count to 5 and no SES!

I've gone through the key sequence about a dozen times now, and it's not popping the SES any more. Codes are cleared, except for the standard P1000.

I'm not arrogant enough to call this a done deal, but I'm cautiously optimistic. Let's see how things go over the next week of commuting.

So, in the end, it was me after all, causing the problem when I R&R'd the PCM.

papadelogan is my favorite person today.

 

Technically it is an insulator, but check out
I don't slather it everywhere but I do use it on the rubber seal in any wiring harness connection I open, and a light coating on the edge of the male portion to help make a good seal as well

 

To me it looks like the dielectric grease is actually helping with the contact, that video is two minutes longer than it has to be, what is it with these guys?

 

They just need a Sous to show them how it's done

 

Ok, final follow-up: a whole week of daily-driving, multiple trips per day, several starts in cold weather without pre-heat (a couple below 32*) and zero SES lights and no codes.

I'm calling this on a "done deal".

Thanks!

 

Like a bad penny...it's baaaaack!

Along with a P1211.

 

P1211 along with the same previous boost code...

ICP sensor? Data logging would show pressure higher or lower than expected.

Or maybe you blew an injector O ring? This could cause high-pressure oil to bleed off, hence a lower than expected reading. The new code. If this happened while driving, you would also have low boost compared to expected readings.

Or maybe you were getting on the go pedal a bit hard when it happened? This could be the chip tune. Commanding more power than the injectors can deliver. Again, low boost (really not truly low) and low oil pressure just because the system is maxed out.

Or the same thing that fixed it 2-1/2 months ago needs to be done again. Probably would start with this.

 

Ok, digging this one up because it's still pissing me off.

Truck has been sitting because of inclement weather (I don't drive it in the ice/snow/salt) but I'm now due for an emissions check this month and need to figure this put. Drove it to work today, key on, get the SES during glow plug warm-up, before start. Fire it up, check codes:

P0237
P1000 (see below)
P0603

I've recently disconnected the batteries (thus the P1000) and completely removed the DP Tuner daughterboard, and - again - removed and reinstalled the PCM.

As noted above, I've:

• Replaced the MAP sensor
• Removed the PCM and MAP sensor rung all wires
• Verified proper voltage at the MAP sensor
• Verified reasonable/rational MAP readings on the Edge controller through various driving regimes

And, of course, after clearing the codes after restart, the codes never ever return with the truck on, only after shutting down and cycling the key, and not always.

Am I looking at a bad PCM here? Who has access to the Ford troubleshooting chart to verify next steps?

Not clear what I'm going to do in regards to emissions. CT will cite me if I can't get this passed, and their wiaver requirements is currently $915 in repairs each two-year emissions cycle.

Greg