Engine/Transmission (1998.5 - 2002) low, then full boost - p0237, p1693 - low power

[TFlewitt]

Started truck to go home last night and had this problem. Have read forum threads, but find nothing like this. Has very low boost - 6-8 psi even at 3/4 - 7/8 throttle. At low/part throttle, boost varies very little, and obviously power is very low. When throttle is open fully, the boost will ramp up and come back up to almost max - 28-30 psi. Shows p0237 and p1693 companion code. Haven't messed with anything lately, no pressure washing, etc. Have Edge EZ. Replaced VP44 almost a year ago. Have the non-electronic "apps" sensor - Timbo sensor - several years old.

If this was a bad map sensor, I would have NO boost, correct? If the terminals (map, Edge, etc.) were dirty, would it manifest in this type of problem? Thanks for your experienced advice!

 

[JR]

Definitely disconnect the Edge and run the truck without it to eliminate that possibility. They tend to be problematic after several years of use.

 

[TFlewitt]

Thanks for your reply. Makes no difference with Edge EZ in or out of the loop. Last night, I could get a little bit of boost at part throttle, then full boost after a few moments when I applied full throttle. Today, there is virtually no boost either way - 2 or 3 lbs. The engine wasn't warmed up today when tested, so don't know if that would make a difference. I found that leaking diesel had filled the map/Edge connectors and disintegrated the Edge to original map plug connector. No effect though after cleaning/repairing/putting back together the connectors. Anyone have any suggestions?

With a defective MAP sensor, will the motor make a little bit of boost. Could someone reply with test for the MAP sensor? Thanks.

 

[JR]

http://www.bluechipdiesel.com/vp44_diagnostics.html

I highly recommend reading the entire page, I don't think you'll find a more detailed diagnostics for the VP44 fuel system. Towards the bottom he goes into detail on how to test the MAP circuit.

 

[Bob4x4]

When the boost sensor starts to fail you will have a very slugish response at low rpm,once you get to the 2000 rpm areait will run close to normal.If you have a boost gauge installed it is very easy to check.Compare your mechanical gauge reading to that seen on a scanner.

 

[TFlewitt]

Did some troubleshooting, but over a couple of days, the symptoms keep changing! The next day, I found that the MAP sensor voltage output was inverted! I have a good 5v signal to the MAP. At rest (with no boost), the output was 1.75v and then as I pushed the MAP diaphragm in, the voltage output decreased to .5 or less volts! A noted Cummins shop said they had never seen this before. Then I put a plug in the MAP hole, left the sensor plugged in (but just hanging there) and I had boost again, although it was a max. of 18 psi. At least it was driveable as I waited for a MAP sensor. The next day (!), now there is practically no boost again (2-4 psi max), with nothing changed, MAP still plugged in and hanging there.

Any suggestions other than waiting to put a new MAP sensor in? The diesel shop suggested the truck may have a bad ECM ground (which I'll check tonight). Anyone had a problem like this? Thanks.