Doug_TX

Okay, I've thown a P0121 code (low APPS voltage). I cleaned out the connectors on the APPS, but haven't gotten to clear the code. But I'm wondering if I have other issues here. Let me explain.

First, ever since I've installed a FP gauge (Q'zilla Commander, and yes, I have the updated sensor) I've had erratic FP readings. Changed from the stock location LP to a Holley Blue pusher located just ahead of the tank. But still have the erratic FP readings (but with ~14 - 16 psi). I also have the dreaded P0216 code too. But when I turn the key to the ON position, I hear the LP bump, but it only runs for (at most) a second. Normally it's just a little 'burp'. So I'm wondering, could there be a problem with the ECM? Could it be sending an intermittent RUN command to the LP? Has anyone heard of this happening? Does anyone know of a source for the APPS? ECM?

crobtex

As you already know, the 0216 is not good and could possibly be causing some of the codes. I don't know that for sure, but it would make sense.

Have you done the APPS Reset and/or Calibration found in the Tech Facts? Either/or one of those might get rid of the P0121.

Don't know anything about the Commander, but sometime a small leak letting air into the line will cause erratic readings.

Doug_TX

Done the APPS reset, but haven't done the recalibration.

On the Autozone site I see a relay called:
Relay - Decelerate Fuel Cut-Off
Can't locate this on the diagram. But if there's a relay shutting off the fuel on decelerate, could a bad (or mis-calibrated) APPS be tellling the ECM that the vehicle is in 'decelerate' mode and cause a shutoff?

And yes, I know the P0216 isn't good. But I'm running good FP now so it might be an old code as I haven't had them cleared.

blackdiesel

My self and one other on here had the 121 and it took a new ECM to fix it. Im not saying that's your problem, but it was mine.

Doug_TX

Given that the APPS is about $475, I can only imagine how painfully expen$ive that was.

crobtex

It's been a few years, but I got my APPS from Cummins Southern Plains for about $336. I'm sure they've gone up, but try a Cummins dealer first.

blackdiesel

Got a used one for $200, and hohn got his under warrenty

Doug_TX

Where did you find a used ECM?

blackdiesel

A salvage yard we do alot of business with found it for me in SC. and had it shipped to me. There is also a guy on ebay that takes apart alot of these trucks called redline, here in AR. that sells them also. Bob wagner on here might have one too.