2008 H3 with 111,000 miles

Been having some goofy battery issues lately, but battery and charging system keep checking out OK. (By the kind folks at AutoZone who would have to give me a prorated battery exchange if it failed...but I saw the readings myself and it seemed to be OK)

Truck went into limp mode this morning before my wife even got out of the garage. Turned it off/restarted a few times and it stayed in limp mode. Then went back 45 mins later and everything is fine, but check engine light still showing.

I took it to Autozone to have the code read and they pulled a P0651 code with the following definition/explanation:

5 volt reference 2 circuit

Explanation:
The ECM has detected an out of voltage range on the 5 volt reference circuit 2

Probable cause:
1. Shorted sensor
2. Shorted circuit condition
3. Failed ECM


The ECM was replaced on this truck < 5k miles ago.

Can anyone point me in the right direction?

 

Are you still using the OEM crappy azzed battery terminal connectors??????

The FIRST thing to point to is those POS terminal connectors. The PCM is sensitive to the tiniest changes in voltage, and the OEM terminals SUCK! There are many, many, many posts on this. Get a good quality aftermarket kit like Stingers. These are on my truck, never a single problem since.



To rule out this simple problem, first thing everybody with an H3 should do id replace the battery terminal connectors. Cheap insurance against electrical gremlins.

 

I'm not disagreeing with you since I've seen this mentioned a bunch...but I'll admit I'm having a hard time understanding how this could be up the issue. I have no corrosion, the connectors are tight, and the crimped connections seem solid. What am I missing?

 

Also, could the battery be doing something intermittently that could be causing this? My wife took it in for an inspection and they told her the battery was acting up, then I take it to AutoZone (twice now) and it's fine.

 

I'm thinking get another battery from Walmart or kmart and test to see if it changes if not you know it's not the problem. I'd replace the oem ends also.

 

You "think/assume" the OEM connectors are tight, every single one of them will fail, just a matter of when. That is what you are missing.

 

While the battery terminals are junk you May also want to swap a battery from your other vehicle and Check if it is the "new" battery.

 

OK, I replaced the battery with a brand new one and yesterday I replaced the terminal connectors with aftermarket ones. All seemed good yesterday, then this morning...same thing! It went into its somewhat violent pulsating limp mode with the errors on the display. Never even made it out of the driveway.

Where would you guys go from here?

 

I would start with a cleaning of ALL your grounds cables and the connections under the fuse block.

Start the truck and play with the cables and connections to see if something is loose or corroded.

 

Well, now that you ruled out the easy stuff, time to move to sensors.

P0651: 5 Volt Reference 2 Circuit fault. This is one of two 5 Volt reference signal circuits that the PCM monitors. There are four components associated with this circuit, any one of which could throw the Code:
1. Accelerator Pedal Position Sensor;
2. Throttle Position Sensor;
3. Crankshaft Position Sensor; and,
4. Secondary Air Injection Pressure Sensor.

#4 is rarely a problem, doesn't usually create your symptoms.

Again, the easy stuff. Check each connector from the harness to #1-4, make sure there is no corrosion and the connectors are snapped all the way on in place. Might want to squirt a dab of electrical cleaner on the connections while you are at it.

If that does not clear it up, time to replace sensors. These trucks do have issues with #1 and #3, they are related to each other and require accurate correlation or you get what you got. That would be my guess.

#1 is about a $40 plug and play, 10 minute job, start there. #2 requires a new TB, and more $$. #3 is pretty darn inexpensive and easy to do as well.

Good luck. Please let us know what you find.