2G 2g ECU sensor ground pin 92 5v?

[Wilsonf4i]

Is pin 92 Sensor ground harness side of the 97 EPROM ECU supposed to get 5v with key on just depinned from the ECU?

I blew the ground in the ECU and had it repaired. I'm doing some troubleshooting to figure out what might've blown my sensor ground inside the ECU. I depinned 92 and I have it connected to my multimeter. with key on it's getting 5v unless I unplug the entire 71 - 92 plug & then it drops down to 0v.

I just need to know is it a 5v reference or is it supposed to be OL (infinit) or grounded .01 ohms if I put my other lead to a good known ground? I read 5v isn't enough to blow sensor ground?

I have multimeter on 92 harness side and I'm pulled these pires with everything connected to the ECU one at a time to see if the 5v goes away. This is the troubleshooting process I should be following?

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[luv2rallye]

Just thought I'd update. Brand NEW TPS is still getting 5v only when TPS is plugged in.

5v where? On ECU pin 92 harness side wire with pin 92 not connected (depinned) to ECU and key on? If yes, that's what you would (and should) see. This is pin 92 harness side wire "floating" to 5v - I don't think you understand "floating" - read Steve's post 5 again. Without pin 92 grounding that wire inside the ECU, the voltage will "float" to whatever the voltage is on the other end of the wire (the TPS power source 5v) - get it?

Also, 5v at 92 ground signal pin when coolant thermostat is plugged in.

Same "floating" concept this time CTS 5v coming from ECU pin 83.

New things I’ve done and need to disclose:

Completely removed & unplugged rear o2 sensor connector/o2 sensor there was severed and exposed.

Ok but now expect CEL codes (like P0136, P0141, P0420).

Verified that with ecu disconnected, no continuity between 2 wires at thermostat and tps signal ground (2, 4) and power wires.

Not sure which wires you're saying. The 2 wires of CTS itself - or some combination of all the many wires (and combinations) of and between CTS and TPS.

Luv2rallye’s comment “You can test if it still goes to ground by unplugging all the ECU connectors and doing a continuity test of ECU pin 92 to it's chassis case. If infinite resistance that circuit trace (or if now replaced with a wire) is most likely melted again.”

-I tested the ground again on ecu it tests good just past the new solder but from the signal ground ecu 92 to the ECU case/fastening screws I get zero continuity. So for sure at least the ground is blown again somewhere else based on your comment? I’m unable to specifically verify the next place to further test the ground on the ecu no obvious new burns.

Don't understand any of what you're saying here. "Zero continuity" means there is no connection yet you say "it tests good". Does your multimeter say 0 ohms or not between pin 92 and ECU case? If not that ECU trace is blown. [Note: Some people when they say "zero continuity" they mean 0 ohms which IS continuity! Zero continuity is NO continuity (zero or none) which is infinite resistance. See the confusion? So which is it?]

Understand that the ground all those sensors need MUST be provided ONLY by ECU pin 92 (for noise and voltage drop reasons). So when you have the ECU unplugged, there is no ground on that pin 92 harness side wire and it will then "float" to whatever voltage is on the other side of those sensors - like 5v.

I still haven't checked the amperage going to 92 5v. I haven't plugged everything back in to see if it'll start since doing all of this and added 2 grounding screws near the ecu connectors that hold the ecu board down.

ECU pin 92 MUST ONLY be connected to ground inside the ECU - no where else (for noise and voltage drop reasons). [Although just temporarily for testing reasons only, you can connect it to any ground - just for testing voltages - but be aware if some sensor has pin 92's wire shorted to a power source, like 5v or 12v, you will burn up a wire, sensor, or something. If you're going to do that just for testing, it's safer to put some resistor in series with the pin 92 wire.]

Perhaps I should buy a new coolant temp sensor to start with? car won't start with a potentially bad one anyway?

Car will run w/o a CTS bad or not.

Just to clarify TPS and or coolant temp sensors being plugged in will cause 5v at pin 92 harness connector (depinned). Goes away unplugged BOTH.

See my earlier comment.

 

[Wilsonf4i]

5v where? On ECU pin 92 harness side wire with pin 92 not connected (depinned) to ECU and key on? If yes, that's what you would (and should) see. This is pin 92 harness side wire "floating" to 5v - I don't think you understand "floating" - read Steve's post 5 again. Without pin 92 grounding that wire inside the ECU, the voltage will "float" to whatever the voltage is on the other end of the wire (the TPS power source 5v) - get it?

Same "floating" concept this time CTS 5v coming from ECU pin 83.

Ok but now expect CEL codes (like P0136, P0141, P0420).

Not sure which wires you're saying. The 2 wires of CTS itself - or some combination of all the many wires (and combinations) of and between CTS and TPS.

Don't understand any of what you're saying here. "Zero continuity" means there is no connection yet you say "it tests good". Does your multimeter say 0 ohms or not between pin 92 and ECU case? If not that ECU trace is blown. [Note: Some people when they say "zero continuity" they mean 0 ohms which IS continuity! Zero continuity is NO continuity (zero or none) which is infinite resistance. See the confusion? So which is it?]

Understand that the ground all those sensors need MUST be provided ONLY by ECU pin 92 (for noise and voltage drop reasons). So when you have the ECU unplugged, there is no ground on that pin 92 harness side wire and it will then "float" to whatever voltage is on the other side of those sensors - like 5v.

ECU pin 92 MUST ONLY be connected to ground inside the ECU - no where else (for noise and voltage drop reasons). [Although just temporarily for testing reasons only, you can connect it to any ground - just for testing voltages - but be aware if some sensor has pin 92's wire shorted to a power source, like 5v or 12v, you will burn up a wire, sensor, or something. If you're going to do that just for testing, it's safer to put some resistor in series with the pin 92 wire.]

Car will run w/o a CTS bad or not.

See my earlier comment.

Until now I've only been checking voltage at ecu 92 unpinned. I back probed 92 plugged in now and it's still 5v. also for amperage I'm getting 0.226A with my multi.

no connection between ecu case and pin 92 ecu. no continuity sorry about that confused statement I made about zero continuity that makes it sound like its good!

None of the sensors along with this ground sensor wire circuit is grounded to the car anywhere.
possibly do you have a recommendation for a resistor I can buy or easily find?
Thank you for chiming in about car will run w/o CTS

I'm going to double check some of my tests today, verify grounding sensor wire circuit is not grounded to car chassis anywhere. and look over the harness today. I'm very suspicious my ecu ground could be bad again it's not burnt and obvious like it was before.
I suspect my coolant thermostat is bad as well. when this all started I had a code for it but i'm just not certain if this was after I started troubleshooting and then caused the code. it tests the same as my other thermostat on the evo 9 and evo 8.

 

[luv2rallye]

Until now I've only been checking voltage at ecu 92 unpinned.

By "ecu 92 unpinned" I'm assuming you removed the single harness wire that goes into ECU pin 92 connector (or removed its connector pin that the wire attaches to) but still have the connector plugged into the ECU - correct? Also all other ECU connectors are still plugged in.

I back probed 92 plugged in now and it's still 5v. also for amperage I'm getting 0.226A with my multi.

Well if pin 92 is "open" inside the ECU, you WOULD see 5v on it [due to either it is (A) floating and getting the 5v from the other side of some sensor OR (B) it is improperly getting a 5v SOURCE voltage (a source voltage does not go through any device but provides the power to run something - like the power for a 5v sensor) which would be a direct SHORT and burn up your ECU trace when grounded].

What exactly do you have your meter wires attached to to read amperage? Can't be in series with pin 92 when its open inside the ECU! If just pin 92 harness wire to ground, 0.226A may not be unreasonable as that may JUST BE THE NORMAL CURRENT TO RUN SOME SENSOR.

no connection between ecu case and pin 92 ecu. no continuity sorry about that confused statement I made about zero continuity that makes it sound like its good!

None of the sensors along with this ground sensor wire circuit is grounded to the car anywhere.
possibly do you have a recommendation for a resistor I can buy or easily find?

New idea: Instead of using a current limiting resistor, I suggest first trying a 12v (6v if you happen to have one) incandescent light bulb (not an LED as they are polarized and need a current limiting resistor anyway) like a dome/foot/marker/turn signal bulb. Attach one side of the bulb to harness wire pin 92 (also attach a voltmeter positive lead on here, and of course the voltmeter negative lead to real chassis ground) and the other side to a real chassis ground. When key on, if the light goes on somewhat you probably have a SOURCE connected to harness pin 92 wire (have some voltage). In that case unplug all the sensors connected to pin 92 one at a time until the light goes out to identify the 5v SOURCE sensor. On the other hand, if it's only a floating 5v from the other side of a sensor (which is normal), I doubt the light would go on at all (near 0 voltage).

If you insist on a "put in series" resistor to do testing, get a 300 ohm or greater one, 1/2 watt. That would protect any direct short from doing damage. Go to a TV (or maybe any electronic) repair shop for one (or Radio Shack if you can still find one).

Thank you for chiming in about car will run w/o CTS

I'm going to double check some of my tests today, verify grounding sensor wire circuit is not grounded to car chassis anywhere. and look over the harness today. I'm very suspicious my ecu ground could be bad again it's not burnt and obvious like it was before.
I suspect my coolant thermostat is bad as well. when this all started I had a code for it but i'm just not certain if this was after I started troubleshooting and then caused the code. it tests the same as my other thermostat on the evo 9 and evo 8.

 

[Wilsonf4i]

An update for whoever is interested:
my consensus is rear o2 wires got ripped out years ago and just now magically they've manage to touch each other and short my ecu ground. I installed a very tiny like 250ma in-line fuse at the ecu and had the ecu re-repaired at ecmtuning. Thank you guys for being so patient and working with me on this scary annoying project.

Btw I didn't want to install a resistor because a tiny fuse just felt like a better choice that also wouldn't effect any of my sensor readings.

 

[2gGSTsquared]

I'm pretty sure the O2 wires wouldn't cause this ground issue even if it DID ground itself magically. I have alldata and I'm looking at the wire diagram from the o2 sensors now, the front and rear o2 share a signal wire from the air flow sensor and ground.

Furthermore, the ground circuit for the 92 pin on the ECU is also shared with front and rear 02's AND the volume air flow sensor, ALL of these grounds end at G302 (behind foot distribution duct), you should check continuity/resistance on your ground from pin 92 to verify ground.

Could the ECU have possibly just have suffered from an old and failed capacitor?

What did ECMtuning have to say about the repair?

IF your fuel gauge isn't working the test per alldata is to
1. Remove fuel gauge unit connector.
2. Connect test light to the harness side connector
3. Turn the ignition switch to ON

4. Check condition of test light AND gauge : IF
a. Test light is illuminated (gauge needle is not moving) --- Replace the fuel gauge
b. Test light is illuminated (gauge needle IS moving) ----- Replace the Fuel gauge Unit
c. Test light is not illuminated (gauge needle is not moving) ---- Repair the harness

Also here is the OHM test for the fuel gauge
Between power supply and ground ..... 249 +/- 30
Between power supply and fuel gauge ..... 127 +/- 25
Between fuel gauge and ground ..... 122 +/- 10