2007 Suburban Reduced Power Engine code
 

Good day all, I have a bit of a brain buster here.


2007 Suburban 1500 LTZ 4wd 5.3 Gas engine code 3


About 5 weeks ago, my wife was driving home and noticed that the Check Engine light came on and the Oil Pressure gauge was fluctuating between 60 & 90 than pegged to 90. She made it home and I did some research and found that I should replace the Oil Pressure Sending Unit. Replaced the part on Saturday afternoon and I must say what a Pain in the #@&^. Everything seemed OK pressure was within normal range. Sunday morning I changed the oil and filter and the vehicle ran fine.


Monday morning my wife called me in a panic, she said that the Oil pressure gauge was again bouncing around but than went to the low side and the car turned off, when she went to restart it the MIL was on, and there was a message saying Reduced Engine Power.


Towed the car home and hooked up the Scanner and was given the following codes (I have the Innova 3100 OBD2 scanner) P0641 Voltage A circuit/open and P0532 A/C Ref pressure sensor A circuit low input.


I speaking with a friend (Ford Mechanic) he said it sounded like electrical problem. I checked the Harness in the area of the driveshaft (common problem for that area to have a problem) everything seemed OK. Replaced the Sending Unit again and still had a problem where the computer kept the vehicle in Reduced Power Mode.


I continued to have the same problem so I started to trace the 5 volt system by disconnecting each sensor one by one and when I came to disconnect the Sending Unit all codes reset and the vehicle started (it sounded fine and ran ok for the few minutes I allowed it too).


I reattached the connector to the Oil Pressure Sending Unit and the codes came back and the car went into Reduced Power Mode


I was told that I needed to use a OEM Sending unit as there were common issues with aftermarket parts. (I also replaced the Valve Lifter Oil Filter little screen under sending Unit that most of the Dealerships I called had no idea what I was talking about). Well on my 3rd sending unit I decided that I did not have enough stress in my life and apparently put too much force on the cheap part and it snapped off. Now I had no choice but to pull off the Intake.


While the Intake was removed I had a straight shot to the Oil Pressure Sending Unit (replaced with a 4th new one) I also decided that I may have damaged the connector while trying to reconnect it blindly so I purchased a new one and spliced it into the existing harness (I soldered each wire, covered with shrink tubing, and then electrical tape).


I checked all of the electrical connections as I reinstalled the Intake and didn't notice any problems. I also replaced the Oil Filter


Car started after I cleared codes, Oil pressure gauge did not move from zero, engine sounded fine but went right back into the Reduced Power Mode and MIL light came back on. Scanner just came up with P0641


Stumped I joined the subscription service that Innova offers and it said that the #1 verified fix would be to replace the Fuel Pump Control Module (FPCM) called the dealer to order the part and they told me according to my VIN my vehicle does not have that part.


Stumped I went to the car and disconnected the Oil Pressure Sending Unit electrical connector and low and behold the car started again and ran fine.


HELP!!!!

Your cheap code reader is giving your red herrings. your truck doesn't have a fpcm, its to old. After the dtc reset, have the codes read by a full function scan tool that can read manufacturer dtc and post them here.

Tech2


I do not do this as a profession so I opted to purchase a middle of the road code reader. The Model I purchased does do manufacturer specific codes. I posted the codes that were listed in the enhanced mode they are the same as the General codes.


According to Chev SI the DTC P0641 5-Volt Reference 1 Circuit ECM


when the Oil Pressure Sending Unit is connected it trips the P0641 Voltage A Circuit/Open when I disconnect the Sending unit the vehicle comes out of reduced power mode and starts/runs ok but trips the P0522 Chev current Engine Oil Pressure Sensor/Switch Circuit Low Input


I'm assuming that the problem is definitely electrical and probably in the circuit with the Oil Pressure Sending Unit. I just can't figure out what is related to these three wires

I have a $200 c reader vi that does all 10modes of obdII...that is miles above anything made by innova.... and mine will still not read certain powertrain dtc that the factory scan tool will.


I'll look into your dtc but at a glance I doubt that an oil pressure dtc would effect anything to cause a reduced power mode. The only thing that comes to mind would be if the oil pressure sensor shares a 5v ref supply with the throttle actuator or app sensor.
I wonder if a p2135 or p1516 is present but your scan tool can't read it.

this is what I found:
The 5-volt reference 1 bus provides 5 volts to the following sensors:

• The manifold absolute pressure (MAP) sensor
• The fuel tank pressure (FTP) sensor
• The air conditioning (A/C) refrigerant pressure sensor
• The accelerator pedal position (APP) sensor 2
• The engine oil pressure (EOP) sensor
• The camshaft position (CMP) sensor

so it is on the 5 volt ref circuit.
there is a tsb to check for chaffed wires near the front prop shaft for this dtc


the 5volt ref wire is shorted at the oil pressure sensor so you will have to locate the short.

Tech2 thank you so much for looking this stuff up for me. I did check for the chaffed wire harness near the shaft and that was fine.


I did install a new Oil Pressure Sending connector from what I could see everything appeared to be intact (there was approximately 5" of wire coming out or a main branch of the harness. I cut the old connector out and left approximately 2.5" of the original wires. I soldered each wire and covered each with shrink tubing). Reading schematics is defiantly a weak point for me.


So if the problem goes away when I disconnect that connector does that mean the problem is in just those three wires or are they somehow linked to the other components of the 5 volt system.


Could a bad sensor cause the problem or is it just a bad wire somewhere.


Thanks again


Joe

one wire...the 5volt ref wire to the oil pressure sensor is shorted to grd. So the short would have to be somewhere between the ecm and the oil sensor connector. probably where the wire goes into a series connection to the sensor.


The way to check for this is to:
key off
-disconnect the ecm connector and the sensor connector
-with an ohm meter connect one lead to the sensor 5volt ref wire and the other lead to grd...there should be no continuity or open. if you get a resistance reading the wiring is shorted.

Tech2


Thank you very much for the information. I will give it a try this afternoon and report back what I find.


Joe

I disconnected the ECM and Sensor checked the 5 volt ref wire and did not get any reading on Ohm meter


I'm lost and open to suggestions this is driving me crazy

Thanks again for your help

actually, thinking about it, it can't be on the 5volt wire if unplugging the connector makes it go away


check the other 2 wires at the connector the same way just to rule them out. I'LL check the diagnostic when I get a chance.

I will check the other two wires shortly.




Thanks


Joe

I pm'ed some testing info for you.

Tech2 thanks for the information in the PM greatly appreciate it.


first off I checked the other two wires and they were fine.


I had a Friend come over to help today and we started the process of elimination


EOP is fine
MAP is fine
ACC is fine
AC :(


got to the AC sensor and did not get 5V at connection I believe <1volt was the reading. Went to the ECM side of it and checked the connections and checked to see if there was 5V coming out of the ECM (no power coming out)


My question is should there be 5V coming out of the ECM going to the sensors, if not is it safe to assume that the ECM is the cause of the open circuit.


Thanks again


Joe

the ac pressure sensor should have 5 volts from the ecm at key in run. It is a 2 wire connector with a grey/white wire that should have 5volts and a tan low ref grd that goes back to the ecm.


If you don't have 5volts at this sensor and you have done the short to grd check like you did on the oil pressure sender and an ohms check shows no resistance in the circuit (I isolate the circuit and put a load on it to make sure the wires can carry current)...if could be an ecm. The testing procedure is to rule out the wiring, if the wiring is ok, ecm is the next step.

Thanks again. Will load test it this afternoon. But it appears to me that not. having 5 V coming out of the ECM ON THE GRY/whi wire tells me there's a problem with the ECM.

Thoughts?

the ecm supplies all the sensors 5volts from the same feed wire. if there is 5 volts on the other wires, the ecm is probably fine.

Still having the same problems and at a standstill.

Tech2 sent you a PM with a question.

Thanks

Joe

Update Got to it again yesterday afternoon and checked each 5 volt connection for short

With the key off and the ECM disconnected I set my DMM to ohms setting and found that I had two connectors that gave a reading other then OL. The APP on the 5v ref 2 side (blk/whi wire) showed 4.43 and the CKP also on the 5v ref 2 showed .3-.4 on the meter

My question is does the reading from the APP mean I have a short somewhere in that wire and also would that cause the ref 1 side to show a problem

Thanks in advance for any help

Joe

I thought the fault was for the 5volt ref 1 circuit?

YUP!!!! That's why I'm completely lost nothing has made sense with this issue from day one. (I went back and checked my notes reviewed any and all Error codes)

I'm going out right now and going to re-test each sensor for voltage, short to ground. Compare all my findings

I have a friend (ford mechanic) helping me and he's stumped too


I'm also going to check the wires coming out of the ECM and see if there is 5 volts coming out (on the connections that showed below 1volt).

They should show 5 volts out of ECM correct?

It is getting close to the " drop back and punt" portion of the repair

the ref 1 and ref2 circuits are separate circuits. So if the fault code is for ref1, forget about ref 2...at least for now.



when you disconnected every 5volt ref 1 connector from the list I posted and checked for 5volts at one sensor. did the voltage drop out at all when the other connectors were plugged back in one at a time?

Found issue in voltage upon connection of the EOP. I sent you a PM with the details

Thanks

Joe

Update
 

Well after about 7 weeks of dealing with this craziness we may have solved the problem. A big thanks goes out to Mike (aka The Cleaner) and Tech2 for their help.

Here's the run down kept receiving a P0641 DTC which indicated an issue with the 5 volt system. And also it put the engine in "Reduced Power Mode" Every check kept leading back to the Engine Oil Pressure Sending Unit. I replaced the sending unit on 5 different occasions 3 from PepBoys 1 from AutoZone (complete piece of Crap snapped while installing) giant PITA to install without taking off the Intake.

Replaced the wiring connection no change still kept tripping the P0641 DTC. After doing some additional testing I decided to make a new wiring harness (found out the hard way) All three wires lead directly back to the ECM connector (in all the schematics I reviewed it showed only 2 wires the gray & black ones going back to ECM) it was assumed that the tan/white went to ground. After a phone call it was found that the wire does go back to ground but through the ECM.

Decided to go with 5th sending unit (OEM) BINGO

SO my Public Service Announcement use only OEM EOP's or you'll regret it.


Joe

when new parts are bad out of the box; it throws a wrench into the diagnostic process. bet it was hard to convince yourself to buy that 5th sensor.


thanks for posting the fix.

Words cannot express what was going through my mind when I decided to go with the 5th sending unit. With everything else that I went through with various testing and procedures it was a good learning experience though

It still would have been nice for the first one or three to work

Thanks again for all of your assistance.

Now onto the problem with my 04 Tahoe will post that shortly

i know this is a couple years old, but my 08 suburban came up with the code reduced engine power, service stabilitrak, and traction control off. I replaced the Throttle body thinking that was it from other research i did about the problem. It wont start now, just keeps turning over but will not run. I have replace my Oil Sender Unit 3 times within the last year myself. My oil pressure seemed good when it was running, but didnt know if you had any other info. I took it to a shop yesterday and they said it was a short and unplugged the Oil Sender Unit and said it worked fine, but they plugged it back and and i tried to start it today and it wouldnt. I unplugged it and it still wont start. I have the PO416 code as well, and thats the only code i have. Any help would be greatly appreciated.