Coolant gauge issue

Wilson2608 · 06-23-2016, 08:53 AM

Quote:

Originally Posted by Jhill

as a journeyman level drivability/electrical diag tech for the last 11 years, up until this last year when finally leaving automotive to actually make a living so I can afford my own z and not fix everyone else, or in my case everyone else's corvette. Loved the work (once I got to a specialized role, no heavy duty, didn't have to do anymore engine R&R or trans etc,) hated the pay and the BS warranty times etc etc.. but I am fairly certain (I'm not there testing so I cant say 100% without a doubt) that you goofed on your wiring. Maybe you screwed up and wired something into the fuel tank pressure sensor? the multiple high voltage codes you have would re enforce my believe that somehow you have screwed up the 5v ref. and the timing of it too.

Okay I'll be reading through the FSM today to gather as much info as I can and see if the two circuits have any common route. Both my codes are high input codes. I honestly think I know what is causing those codes though. When I depressurized the fuel lines I didn't unplug the fuse. I just unplugged the fuel pump and cranked the car. Yeah obviously that will throw a Cel and I knew that from the beggining, I just figured it doesn't matter and it'll be fine once I clear the codes. I bet that has something to do with the short or wiring issue. So basically, to test for the 5v reference I can use my multimeter at certain sensors and test for the 5v power supply?

Wilson2608 · 06-23-2016, 10:03 AM

On my way to work this morning both the fuel gauge and coolant temp gauge started working fine. So weird..

Im sure the gas gauge is still off due to what I had to do in order to get the fuel pump housing top and bottom to hook up right, but at least its reading.

Only issue now is I still have the CEL and the car tends to idle a little high. (1100 rpm) I think thats due to the fuel temp sesnor code.

Like I said before ill check the fuel temp sesnor wiring for shorts and post back!

SouthArk370Z · 06-23-2016, 11:45 AM

Quote:

Originally Posted by Wilson2608

... So basically, to test for the 5v reference I can use my multimeter at certain sensors and test for the 5v power supply?

Please get some help before you kill some electrical component(s) or start a fire.

But, yes, a decent multimeter and tools to access the wiring/sensors should be all you need. I'm guessing that the problem will be pretty obvious with a visual inspection.

I haven't looked at the wiring diagrams but the 5V reference that Jhill refers to may be internal to the ECM. If so, you will need to check it at the ECM (if possible). If the outputs from the sensors are out of spec (I'm betting that will be the case), the reference is probably not the problem. The 5V ref is just a possibility. I think (and it seems that JHill agrees) that the wiring/sensors is the most likely culprit.

Jhill · 06-23-2016, 12:09 PM

Quote:

Originally Posted by SouthArk370Z

Please get some help before you kill some electrical component(s) or start a fire.

But, yes, a decent multimeter and tools to access the wiring/sensors should be all you need. I'm guessing that the problem will be pretty obvious with a visual inspection.

I haven't looked at the wiring diagrams but the 5V reference that Jhill refers to may be internal to the ECM. If so, you will need to check it at the ECM (if possible). If the outputs from the sensors are out of spec (I'm betting that will be the case), the reference is probably not the problem. The 5V ref is just a possibility. I think (and it seems that JHill agrees) that the wiring/sensors is the most likely culprit.

You're pretty safe to check it as the ECM typically have their own resistor in series before the output and that is how they determine a dead short or open as the sensors operating is typically .7-4.5 so if it sees 0 or 5 it know there is an open or short. On sensors that have a sig return it's a little different and if you screw the ref up well like the saying goes garbage in garbage out. Before you even venture in this journey I would highly recommend you pull those codes and get the wiring diagrams that go with those systems. Without proper documentation you are just guessing.

SouthArk370Z · 06-23-2016, 12:47 PM

Quote:

Originally Posted by Jhill

You're pretty safe to check it as the ECM typically have their own resistor in series before the output ...

IF the person using the meter knows what they are doing. Even if the ECM is bullet-proof, I'd hate to muck around, short some wires, and put 12V where it doesn't belong (like inside the gas tank). If it were you doing it, I wouldn't be too concerned - I'm not sure OP has acquired the skills to do the job safely.

Jhill · 06-23-2016, 02:55 PM

Quote:

Originally Posted by SouthArk370Z

IF the person using the meter knows what they are doing. Even if the ECM is bullet-proof, I'd hate to muck around, short some wires, and put 12V where it doesn't belong (like inside the gas tank). If it were you doing it, I wouldn't be too concerned - I'm not sure OP has acquired the skills to do the job safely.

Too true. I've seen so called master techs do **** that I still shake my head at. It can be scary out there.

Wilson2608 · 06-23-2016, 03:09 PM

Both of you are obviously very knowledable about cars/ electrical work, and i basically know little to none about this kind of stuff. But im adament about doing the work myself for the purpose of becoming more educated. When my engine blew in my 300zx I took it upon myself to do a motor swap. It took me like 2-3 months, but eventually i got it perfect with no issues at all. And now i could do it in half that time, and thats the reason I want to fix this issue too. I will follow the procesdure in the FSM so I don't mess anything up and i'll let you guys know!

Thanks so much for help mates

Jhill · 06-23-2016, 05:21 PM

Quote:

Originally Posted by Wilson2608

Both of you are obviously very knowledable about cars/ electrical work, and i basically know little to none about this kind of stuff. But im adament about doing the work myself for the purpose of becoming more educated. When my engine blew in my 300zx I took it upon myself to do a motor swap. It took me like 2-3 months, but eventually i got it perfect with no issues at all. And now i could do it in half that time, and thats the reason I want to fix this issue too. I will follow the procesdure in the FSM so I don't mess anything up and i'll let you guys know!

Thanks so much for help mates

Dumb ? What's this FSM everyone is referring to? Are you guys getting access to the wiring diagrams?

SouthArk370Z · 06-23-2016, 05:35 PM

Quote:

Originally Posted by Jhill

Dumb ? What's this FSM everyone is referring to? Are you guys getting access to the wiring diagrams?

Factory Service Manual. See link in my sig. Merry Christmas. The wire color codes are not always intuitive.

06-23-2016, 10:03 AM	#2 (permalink)
Wilson2608 Enthusiast Member Join Date: Dec 2014 Location: Nashville Posts: 301 Drives: Nissan 370Z Sport Rep Power: 12	work On my way to work this morning both the fuel gauge and coolant temp gauge started working fine. So weird.. Im sure the gas gauge is still off due to what I had to do in order to get the fuel pump housing top and bottom to hook up right, but at least its reading. Only issue now is I still have the CEL and the car tends to idle a little high. (1100 rpm) I think thats due to the fuel temp sesnor code. Like I said before ill check the fuel temp sesnor wiring for shorts and post back! __________________ Stillen G3, z1 Intake Manifold, Stillen Headers, Z1 HFC's, Stillen Catback. 330whp 267 ft- lbs tuned at Z1 motorsports.

06-23-2016, 03:09 PM	#7 (permalink)
Wilson2608 Enthusiast Member Join Date: Dec 2014 Location: Nashville Posts: 301 Drives: Nissan 370Z Sport Rep Power: 12	:) Both of you are obviously very knowledable about cars/ electrical work, and i basically know little to none about this kind of stuff. But im adament about doing the work myself for the purpose of becoming more educated. When my engine blew in my 300zx I took it upon myself to do a motor swap. It took me like 2-3 months, but eventually i got it perfect with no issues at all. And now i could do it in half that time, and thats the reason I want to fix this issue too. I will follow the procesdure in the FSM so I don't mess anything up and i'll let you guys know! Thanks so much for help mates __________________ Stillen G3, z1 Intake Manifold, Stillen Headers, Z1 HFC's, Stillen Catback. 330whp 267 ft- lbs tuned at Z1 motorsports. Last edited by Wilson2608; 06-23-2016 at 03:41 PM.

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