Question: Grounds

[John Robinson]

I have been trying to find were all the electrical grounds are located using my FSM. So far I have not been able to find that information. The FSM wins on this one it has kept it's location a secret from me. ;help

 

[vetteoz]

Main engine harness grounds are on a big bolt ( 3/4" head ) in the block above the oil filter .Looking at the FSM it looks as if the internal grounds go there as well.There are several other smaller grounds under the dash
Ground back to battery is from cable (- neg ) fitted to bellhousing bolt on pass side

 

[toptechx6]

Check book #2 in the Electrical Diagnosis Chapter, section 8A-14, Ground Distribution.
Note that for ALL wiring diagrams location of components, grounds, splices and connectors are specified at the end of each wiring section.
Grounds are specified with the letter G followed by a 3 digit ID number, spices use "S" and a 3 digit ID number, connectors use the letter "C" and a 3 digit number.
You will find the location of all grounds on page 8A-14-15, hope that helps.
The 201-PG heading at the top provides graphic help to locate components, splices, connectors and grounds, section 201 is near the end of book #2 , it consists of illustrations showing the above items.
The "CONN" heading , section 202 follows the illustrations showing location, the purpose of section 202 is to visually identify each connector in the wiring diagrams.

 

[John Robinson]

Thanks

Senior moments are frustrating thanks for the information. I have been having an issue with poor gas mileage and on the slab I get an SES with codes 55,63,64. Also the engine seems to be running rough at road speed and above say to over 120. As for the balance of the tires they have been done so many times the car just automatically pulls into the tire shop when I go by. I did find in the FSM the section that talks about faulty grounds or vacuum problems will cause these symptoms. But before that I had advice from Junk to check for vacuum leaks. He also has been an advocate of fixing corroded grounds to clear up a lot of problems so here goes.

 

[Robertwav1]

Along the frame rails both sides under the hood, if you look along the rail you will see them, 3 or 4 from what I can remember. Also under the car, bell housing there is at least one and also frame rail drivers side under vehicle....again from memory when I redid all of mine. 1993

 

[Hib Halverson]

First of all, what manual are you using that suggests bad grounds as a solution to DTC 55?

That code deals with the fuel supply system. See page 6E3-A-88 then run the fuel pressure tests it suggests along with the rest of the diagnostic instructions.

DTC 63 is an open in the right O2S circuit. It could be a wiring and connections issue but it also can be a faulty ECM. See page 6E3-A-92 for more instructions and follow them to the solution.

DTC 64 is lean exhaust on the right bank.

My wild-assed guess is that, if the fuel pressure testing shows the fuel supply system to not be fault, then the problem is erroneous lean exhaust readings from a problematic O2 Sensor circuit on that right bank.

It is possible there's a problem with grounding but, because you don't have the same problem with left sensor, I'd look at other causes first. Run the fuel system tests to determine if DTC55 is really current, then solve DTC63. If you find an repair problem in the solution to 63, then I'd clear codes and road test to see if any of those three come back.

On the other hand if you verify that DTC 55 is a legitimate fault, then I'd repair that problem first (ie: new fuel pump, new fuel filter or other fix) then clear codes and road test to see if the other codes return.

 

[John Robinson]

First of all, what manual are you using that suggests bad grounds as a solution to DTC 55?

As I said when I posted I am using the FSM which I believe is the universal abreviation on this forum for the GM Field Service Manual.

DTC 55 page 6E3-A-89 first box clearly states that before doing the fuel pressure check to go to DTC'S 44 or 64 if they are set along with DTC 55. It was not until my second post titled Thanks that I mention the codes I had. As for my saying that bad grounds with DTC 55 was the cure for my problems I would like to point out that I did not make such a statement in my original thread or my follow up post.

I will address the DTC 64 issue next as it was suggested in the DTC 55. DTC 64 page 6E3-A-94 under Diagnostic Aids it says to check for intermittent ground wire between connector and sensor. I believe that establishes that intermittant grounds can be the first area to check. Also note on page 6E3-A-95 it also refers to diagnostic aids which just reinforces the need to check grounds.

At this point in following the notes and path set forth in DTC 55 before proceeding with DTC 55 diagnostic procedure DTC 64 must be resolved first.

That code deals with the fuel supply system. See page 6E3-A-88 then run the fuel pressure tests it suggests along with the rest of the diagnostic instructions.

DTC 63 is an open in the right O2S circuit. It could be a wiring and connections issue but it also can be a faulty ECM. See page 6E3-A-92 for more instructions and follow them to the solution.

Now we go to DTC 63 page 6E3-A-93 and following the chart to the first Yes box were it refers to the Diagnostic Aids on the facing page. This Diagnostics Chart refers to the intermittant section 6E3-B

In 6E3-B-2 Under the Visual/Physical Check it offers several checks to do before jumping into the DTC Diagnostic Charts.


DTC 64 is lean exhaust on the right bank.

My wild-assed guess is that, if the fuel pressure testing shows the fuel supply system to not be fault, then the problem is erroneous lean exhaust readings from a problematic O2 Sensor circuit on that right bank.

It is possible there's a problem with grounding but, because you don't have the same problem with left sensor, I'd look at other causes first. Run the fuel system tests to determine if DTC55 is really current, then solve DTC63. If you find an repair problem in the solution to 63, then I'd clear codes and road test to see if any of those three come back.

On the other hand if you verify that DTC 55 is a legitimate fault, then I'd repair that problem first (ie: new fuel pump, new fuel filter or other fix) then clear codes and road test to see if the other codes return.

At this time I have not done anything with the grounds because of the 10" of snow here. However I have gone over the vacuum and I belive I found a loose vacuum connection which I solved temporally with the result that the gas milage has started to improve even with the temp in the 7. Along with that the performance is dramically better.