Bad Alternator

cxkali

Original poster
Member
Jan 20, 2012
125
would it be possible for a bad alternator to cause the reduced engine power light to come on as of right now mine is only putting about 70amps have a thermal clutch fan with the code p1515 and I think it was a p1221.


sorry put this in the wrong section.
 

mrphoenix80

Member
Jan 1, 2013
251
the p1515 code asks if you have a p1221 if so diag that first.
P1221 runs if battery volts is above 5.5 volts so I dont think the alternator could cause it because if your battery volts are that low the truck is not running( not enough power to run the fuel pump or fire the coils)!
There are a few bullitins to check your 5v ref lines because one could be pulled low and setting codes.
Other than that these code are for a disagreement between throttle position sensors 1&2. So it could be an internal fault of the throttle body, But make sure your 5v reference voltage to the sensor is good first.
 

seanpooh

Member
Jan 24, 2012
461
When I had my bad alternator, I didn't have any codes or REP. What I did have is that red battery light on and my DIC telling me that my battery was not charging. I wish I could help more...
 

CaptainXL

Member
Dec 4, 2011
2,445
Mrphoepnix is on the right track. This is a common issue and it seems like it comes up every few weeks or so.

Basically what you have is a short in the 5 volt reference wiring. This 5 volt circuit is common to both the throttle body position sensor and the fan clutch. Hense the reason for the two codes.

You will more than likely find exposed wires, (right before it enters the fan clutch assy) which have been rubbing against the plastic mount. This has been documented as an issue with some fan clutches, that the protective sleeving for the wires does not extend far enough to protect it from this rubbing.

Replace/repair the harness to fix.
 

cxkali

Original poster
Member
Jan 20, 2012
125
i changed my clutch fan to a newer 08 model so i know its not the clutch fan so im not sure what it could be. i may need a new throttle body after all.
 

meerschm

Member
Aug 26, 2012
1,079
Where are the wires that used to go to the fan clutch?
 

cxkali

Original poster
Member
Jan 20, 2012
125
ive got it wrapped in tape and taped it to the battery holder bar.
 

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