So I've been chasing a stall problem that was somewhat intermittant that has become an almost daily occurence. Vehicle is a 2006 Dodge Ram 1500 SLT QC SB 5.7L Hemi MDS 545RFE 4x2 3.55 gears 137K miles.
Changed most of the plugs (12 of 16) last Sunday. Will do the remaing 4 (the toughest to access) this Saturday. See the Spark Plug thread in the Ram forum (http://www.allpar.com/forums/topic/139430-spark-plugs/
Thought that might cure the stalling problem which usually only happens on cool/cold mornings. It'll stall or nearly stall at the first stop within a mile or so of the house. Refires with no problems. Could actually feel the engine stumble as I slow to a stop. Changing the plugs made no difference. Even though the CEL was not on, I stopped at Advance Auto last night to have them check for any fault codes that may be stored, but not triggering the CEL. I was inclined to think the EGR was going bad (replaced at 83K).
Imagine my surprise when the code reader found this:
P1521 - Incorrect engine oil.
As I had the last oil change done by the local Firestone shop, I checked the service invoice and it says they used 5W-20 which is the recommended weight for the Hemi with MDS. Hmmmmmm...... The more I thought about it, the stalling became more prevalent after the last oil change and has become progressively worse with the cooler weather (ambient temps around 40*F in the morning now).
Since an oil change was due (last done at 133K and the truck has 137K now). Put in Castrol 5W-20 (7 qts) and a Purolator filter. First time in a long time I did an oil change after dark (yes, I do have work lights). Maybe it was just me, but the engine sounded smoother after the change and guess what - it did not stall this morning!
So that brings to mind - what was wrong?
1) Did Firestone use the wrong weight oil (10W-30) even though the service invoice indicates 5W-20?
2) Oil pressure sensor going bad (the gauge has been normal as far as I can tell)?
3) Anti-drain valve in the filter failed?
4) Just a quirk?
I'm inclined to send a sample of the oil to a tester to verify it was the proper grade- if that indeed can be tested for(?). If not, I'm going to have a talk with the Firestone manager.
I know the proper grade is critical for the MDS (Multiple Displacement Service) to operate correctly so I generally do oil changes myself or at the dealer. I've never seen this code come up before nor did I have stalling issues like this (EGR issue aside) - it did not stall everyday when the EGR was bad (P0406) though it did eventually set the CEL.
Googling the web I found a P1521 could be two different issues depending on the vehicle:
1) Incorrect Engine oil or
2) Transmission Engaged at High Throttle Angle
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