Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!

1 - 20 of 30 Posts

·
Registered
Joined
·
117 Posts
Discussion Starter · #1 · (Edited)
Just got a p0652 code which put me into limp mode. Ladies wanted me to wake up the neighborhood so I gave it about 85% throttle getting on the highway and I went into limp mode. Pulled over and put it in park and it started to sound like a lope tune and like it was about to die if I didn't give it any gas. Cleared the code and its out of limp mode and no more codes as if all problems are gone? What does this mean and am I going to hurt anything to drive on it now? Got me all worried any input is appreciated
 

·
Premium Member
Joined
·
154 Posts
Hey Carter, did some digging for you on this one and found some discussion in the archives on this forum. This post is from Canadian Cowboy in response to someone having similar issues. The first line is in reference to his A/C blowing cold/hot intermittently. The rest of it is relevant unless you have been having similar issues.

"Repair the wires on the A/C high pressure switch.
Here are the reasons a PO652 code will set.

P0652 5-Volt Reference 2 Circuit Low Voltage
Possible Causes Setting Conditions

5V reference circuit is open or shorted to ground
One or more of the devices (listed above) that connects to the circuit has failed
ECM has failed

Engine running; and the ECM detected the 5v Reference 2 signal was less than 4.70v for 2 seconds. This VREF circuit connects to the Engine Oil Pressure (EOP), A/C Refrigerant Pressure (ACP) sensor and the Fuel Rail Pressure (FRP) sensor. These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore, a circuit fault on one 5-volt reference circuit may affect other sensor 5-volt reference circuits. The ECM monitors the voltage on the 5-volt reference circuit.

This code sets in 1 Trip(s).
This code will turn on the MIL (Malfunction Indicator Lamp)"

I'll check around some more and see if any more info is available, but it's probably a bad connection. I'd check wires and connections to the ECM, FICM and see if anything is obvious. (Bare Wires, Connectors Seated Properly) You're going to throw that code whenever the problem rears its ugly head....could be a day, week, month, year...more than likely the most inopportune time..haha.

Good Luck,
Bob
 

·
Premium Member
Joined
·
154 Posts
OH, I forgot to mention, I have an LLY...I have experience with electrical problems...
 
  • Like
Reactions: PauLLY

·
Registered
Joined
·
117 Posts
Discussion Starter · #5 ·
Thanks for the great info bob! That helps me rule out some much scarier problems that I was worrying about. So it's the wiring of one of those things, but just to make sure, a low rail pressure couldn't cause that could it?
 

·
Premium Member
Joined
·
154 Posts
I think low rail pressure is a result. I'm digging around right now on some TSB's. There is one I found, not sure if specific to the LBZ, and is outside the box of the 0652 code, but while you are checking wires, check your Vane Position Sensor wire and make sure it hasn't rubbed clean on the doghouse of the turbo.

Does the Edge show Act vs Desired pressure? I don't have one and don't know. I'd bet that there is a fault in a wire causing one of the 5 sensors to kick low voltage...I'm sure there is a cascade effect through the ECM that will screw fuel pressure. That's the only code you have, right? Low Rail Pressure code is P0087.
 

·
Premium Member
Joined
·
154 Posts
But to answer your question, I believe it can. Not sure if Rob eliminated the activation of the MIL due to low rail pressure out of your tuning or if that's even a good idea. If you didn't pop a P0087 then I'd bet we're on the right track.

How aggressive are your tunes?
 

·
Registered
Joined
·
7,336 Posts
What will you do the next time the ladies want you to wake up the neighborhood :eek:. more :gearjamin
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #9 ·
What will you do the next time the ladies want you to wake up the neighborhood :eek:. more :gearjamin
I'll limp that SOB one more time!:D
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #10 ·
But to answer your question, I believe it can. Not sure if Rob eliminated the activation of the MIL due to low rail pressure out of your tuning or if that's even a good idea. If you didn't pop a P0087 then I'd bet we're on the right track.

How aggressive are your tunes?
Opt. Stock
Heavy tow 30 hp
Light tow 60 hp
Drive 90 hp
Race 120 hp

I haven't ever run the 120. I always run the 90 out of trans damage fear
 

·
Registered
Joined
·
7,336 Posts
Opt. Stock
Heavy tow 30 hp
Light tow 60 hp
Drive 90 hp
Race 120 hp

I haven't ever run the 120. I always run the 90 out of trans damage fear
You could still have trans issues even on 90, depending on the lead foot.
I'm pretty sure SFSMAJ18 is on the right track on the cause.
Recently there has been a few having the fuel issues, it was recommended that they installed a lift pump.
The way to find out is to drop the tune to a lower setting if you don't have a problem, then it's the fuel supply.
 

·
Premium Member
Joined
·
154 Posts
Ok, Yeah, I'm putting my money on a short...Batteries are in good shape I assume? I would check the wires coming off all those sensors and trace them back to the ECM. I'm not the most proficient at EFI live, (working on it) but I believe you can check the voltage outputs to those sensors as well, which may help isolate the issue.

Anyway, good luck. Might be a beer or two project.
 

·
Premium Member
Joined
·
154 Posts
I agree with D_R_C on the trans "safe" aspect of the tuning. 90 is pushing it on a stock trans. I just had mine built last week...had 230k on it so it did its job and wasn't trashed, but wasn't as strong as it had been. Night and day difference. Hang on to your wallet and don't whine about getting new tuning....haha.

With respect to your fueling...If you had popped a low rail pressure code (P0087), then I would steer you toward a shim kit for your rail or a lift pump. Since that isn't the case, then there sensors that are not receiving 5v somewhere, are angry about it, and are throwing your CEL on. Find the cause of that lack of voltage. (Bad ground from Batteries, bare / shorted connection to one of the sensors)

Someone else may have already solved this one before. It is literally on every forum, thousands of posts, nothing really specific as a solution other than what we've been talking about from what I get from it.

Do you have a V2 cable?
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #14 ·
Is that just the regular efi live tuner pod? If so then yes. Tomorrow I'm getting down and dirty with a voltage meter
 

·
Premium Member
Joined
·
154 Posts
The V2 cable links your EFI tuner or laptop to your OBD port for scanning / flashing. Hope your find the source.
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #16 · (Edited)
So I just got limp mode again today. Does this help anyone with advice?



 

·
Premium Member
Joined
·
17,806 Posts
Moved to LBZ for more help
 

·
Registered
Joined
·
96 Posts
Just asking was the truck fully warmed up before beating on it?
 

·
Premium Member
Joined
·
154 Posts
I think he got it handled. Bad FRPS.
 

·
Registered
Joined
·
112 Posts
Problem solved. No more disappointed ladies
 
1 - 20 of 30 Posts
Top