Okay, my truck has a way of throwing new things at me just when I plan on using it to haul something and have a schedule to keep!

The last couple of short drives, I noticed the CEL come on, but it went away when I turned off the truck and then let it cycle through its checks on start-up. Today, however, it came on and stayed on. I didn't think I could feel anything different about the truck's behavior, and since I've been doing local windy/mountain road driving, I never get out of 3rd gear anyway, so wasn't detecting any obvious loss of power.

Thankfully, I had my code reader with me, so I pulled one code: P0237, "turbocharger/supercharger boost sensor A circuit low". After that, on my way home, I thought I couldn't hear the turbo winding like it usually does.

I did a search on that code here and got a few threads discussing the map sensor. On those threads people talked about power drops but not necessarily CELs coming on. Could my situation mean some other diagnosis? Sure would be nice if it was a simply sensor replacement. Is the MAP sensor something I can get at a local parts store, or is it something I'll need to order online?

Also, is this something that is bad to drive with? My horses are about out of hay and I was due to go get a load on Thursday! What other possibilities might this be?

Thanks!

 

The wastegate could be stuck open hence the low reading code.

 

Probably have to get the MAP from Cummins or Dodge.

 

Whatever the cause, the CEL went out without my doing anything. Makes me nervous since I know it will come back at the most inopportune time!

I have muddled my way through fixing various things on this truck in leu of spending lots of $$ at a shop, but I must admit I hardly know my way around the engine. I couldn't even figure out where the Map sensor was... is it somewhere around the stock fuel lift pump location? I thought I saw something down there that looked a little like the picture in the Haynes guide....

Betsy

 

P0237 does turn on the check engine light as you found. It will also put the engine into "Limp Mode" and will cut engine output above 1800 RPM.
The ECM expects the MAP sensor to always have its output voltage between 0.5 and 4.5 volts. The P0237 code for low voltage can only be tripped if the sensor is failing or if the connector to it is not making a good contact. It may also be caused by a problem in the wiring harness between the sensor and ECM.
If I were trying to fix this I would start at the MAP sensor connector. It is not uncommon for dirt or corrosion to cause a problem connection. Radio Shack sells a product to clean and protect metal connections called Deoxit. This product has two small spray cans, one to clean and one to prevent further corrosion. I have use it successfully to keep my truck working.
Good luck.

 

This truck is driving me mad. Maybe this additional information will help...

Summary:

1. Last year OEM pump periodically dropped pressure. Bought a FASS DDRP which I installed this August b/c the OEM went back to behaving until then.

2. DDRP performed perfectly for a month, then one day 0 pressure. Thought it had died. Put the old OEM back in and it behaved again!

3. However, OEM pump started dropping pressure regularly, hanging at 2 psi. Found a wear spot in a wire near the pump harness; wrapped it with electrical tape, got regular pressure again. For awhile...

4. Last week, CEL came on and got the P0327. On the way home, pressure dropped to 2 psi again.

5. Yesterday, I re-wrapped w/ new tape, got regular pressure. Next start up, pressure dropped. So, I swapped out the wiring harness with one I had ordered for this, to cut out the wear spot. Started up, still no pressure. Figured old OEM pump had finally died. Figured the DDRP hadn't really died, was the short, so reinstalled it. Pressure shot up - yeah, fixed!!

6. Picked up a friend's trailer, truck ran fine. Had trailer wiring problems so we fought that for awhile. I turned on the ignition, and there was the CEL again! Went to bed to fight this later...

7. Today, started up, CEL still there, AND pressure at 2 psi!!!

8. Checked banjo bolts, tight. Checked the plug into the pump, fine. Pulled the wire from the MAP sensor, wiped off the connector. Turned on, pressure shot up!! CEL off!!! However, code still there. Turned truck off.

10. Decided to do a test drive, turned on truck, pressure at 2 psi, CEL back!!

Okay, are these things related? Does the MAP sensor having anything to do with the electrical to the pump? Obviously, both pumps can't be bad: it's got to be the electrical to the pump, but why the PO327 at the same time?

All the while, I've had no dead pedal or power deficiencies that I'm aware of.

One more note: tonight, when I turned the ignition on (but hadn't started the truck) the usual chimes range, but there was a secondary "note" chiming at the same rate, never heard this before. Sort of a sub-ding sound, or a vibration matching the frequency of the chime, couldn't really tell.

I read somewhere that cleaning the MAP sensor wouldn't help if it were throwing the P0327. I don't have any carb cleaner; what else would work?

Thanks! O'Reilly's has a MAP sensor coming in tomorrow morning but I don't want to get it if there's still more options. I'm about ready to throw in the towel and take it to a shop, either that or lose my marbles...

Betsy