how to test sensor ground?

[2.0L_turbo]

Hey guys, 

I made a plug and play adapter for my link storm X to connect straight into my 91 Eagle Talons harness. For the most part it works awesome but I am having an issue where my TPS and my map sensor are not working. At first I thought the map sensor wasn't working because I had made a adapter harness for that to plug into the factory mas air flow sensor connector on the engine harness side, so I checked to see if the harness had continuity and power being delivered on all appropriate pins, which it did. But then I noticed that my TPS was also not functioning and with both being AN volt and using a sensor ground I got suspicious that maybe the issue is actually the sensor ground not working as it should. I know my TPS is functional as it works just fine on the stock ecu however the map sensor never came on this car so I was tapping into the sensor ground for the MAF sensor but I also used that sensor ground for the IAT sensor and that is working just fine. And yes I did calibrate the TPS and it sits at 0.01 and MAP shows 0.00

 

So with all that said how can I go about testing the sensor grounds to see if maybe they are my issue. If needed I can attach a tune file but the car has not started yet so there is no real log just the evo base map.

[Adamw]

With ign off if you measure between the sensor ground pin and battery negative with an ohm meter you should see near 0ohm.  

 

[2.0L_turbo]

12 minutes ago, Adamw said:

With ign off if you measure between the sensor ground pin and battery negative with an ohm meter you should see near 0ohm.  

 

is there any other tests I can do along with this one to figure out why the TPS is not working? 

[Adamw]

You could unplug the sensor, watch the analog input voltage in PC Link, it should show 0.00-0.02V when unplugged, then bridge the 5V pin to the signal pin in the TPS loom/plug, the AN Volt should then show 4.98-5.00V.  If it doesnt that would suggest there is a wiring issue somewhere.  

[2.0L_turbo]

Ok so update,

 

Just tested sensor ground as you asked, I did it with stock ecu and the link set up. On all tests at the maf plug, my loom, and TPS all are the exact same at 0.02- 0.03 ohms. My next question should the signal wire for the map be outputting more voltage then the 5v+ wire? With the ignition in the on position I am getting 2.2mv on the 5v+ and 7.2mv on the signal wire for the map sensor. And TPS is seeing 1.7v

[2.0L_turbo]

8 hours ago, Adamw said:

You could unplug the sensor, watch the analog input voltage in PC Link, it should show 0.00-0.02V when unplugged, then bridge the 5V pin to the signal pin in the TPS loom/plug, the AN Volt should then show 4.98-5.00V.  If it doesnt that would suggest there is a wiring issue somewhere.  

ok so I tried to do this but I am not sure if the value I am seeing is what you are looking for to go to 5V. I believe I seen a post you had commented on showing a picture of a tab in link that displayed analog input voltages but I do not see that on mine. here are some screenshots of what I got when I bridged the two as well as what is is when the connector is plugged in. 

 

connector plugged in

 

connector unplugged

 

 

connector bridged

 

hope that helps

 

[Adamw]

This should show 5V with the 5V pin bridged to the signal pin.  Since it is only showing 1.21V suggests you have a wiring issue.  Do you measure 5V at the TPS plug?

[2.0L_turbo]

8 hours ago, Adamw said:

This should show 5V with the 5V pin bridged to the signal pin.  Since it is only showing 1.21V suggests you have a wiring issue.  Do you measure 5V at the TPS plug?

Yea I measured that and was seeing 1.7 ish volts. Thinking I may bypass the factory harness for map and TPS and make a sub loom 

[2.0L_turbo]

Ok so an update, I remade my map/iat harness and added in TPS and ran them directly to the ecu and ran all the tests again. Thankfully this time it worked! 

 

 

So now I was able to calibrate my map and TPS for the first time successfully and saved it to the ecu. Tried firing up the car and it started but dies seconds later. I will add a file of the tune in a hour or so and hopefully see if there is anything I'm missing.

[2.0L_turbo]

Here is the file from when the car starts runs for 2-3 seconds then dies, any help on this would be greatly appreciated.

talon 1.pclx

[Adamw]

Can you do a log of a start attempt.  Stalling after a few seconds would often indicate there is not enough fuel so it is only running when the extra pre-crank prime and crank enrichment fuel is being added. 

What size injectors does it have?  

[2.0L_turbo]

injectors are 550cc low impedance running resistor ballasts, I can try and take one later tonight when I get off work. for the errors I am getting is it safe to set high and low voltages to 0 and 5V? 

[Adamw]

Your master fuel will need to be much higher for 550cc injectors, I would try it up around 20-25ms.  

 

3 hours ago, 2.0L_turbo said:

for the errors I am getting is it safe to set high and low voltages to 0 and 5V? 

The only error you have in the map above is for AN Volt 3 (TPS) being above the error high.  But that shouldnt happen if the wiring is ok and TPS is working correctly.  If you clear the codes, what causes it to come back?  

[2.0L_turbo]

2 hours ago, Adamw said:

Your master fuel will need to be much higher for 550cc injectors, I would try it up around 20-25ms.  

 

The only error you have in the map above is for AN Volt 3 (TPS) being above the error high.  But that shouldnt happen if the wiring is ok and TPS is working correctly.  If you clear the codes, what causes it to come back?  

I'm about to take a log is there anything specific your looking for that I should add?

[Adamw]

Do a PC log, it records everything.  

[2.0L_turbo]

here are some data logs i had it idling for a min or two but the idle was really high around 2500rpm, tried cycling the ignition and then it went back to dying on start up. what the fuel number is referring to is the master fuel ms 

talon fuel 15.llgx talon fuel 18 no isc.llgx talon fuel 18.llgx talon fuel 20.llgx talon fuel 22.llgx talon fuel 25.llgx

[2.0L_turbo]

just curious if anyone has had a chance to take a look at these logs, really hoping to get to do some tuning with the car next weekend

[Adamw]

Cant really see why it is stalling.  It appears to be running ok then suddenly goes lean and stalls.  The injector PW doesnt change when it goes lean so the ecu is still commanding the same amount of fuel.  

What controls the fuel pump in these things?  Could the fuel pump be stopping?  Is there fuel pressure?  

[2.0L_turbo]

 

 

the fuel pump is controlled by the MPI relay, here is a link to another forum explaining what all the mpi does and how it operates, but I can keep the car running if I give it throttle it just wont stay running on its own right after the initial start up.

 

https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/ 

58 minutes ago, Adamw said:

Could the fuel pump be stopping?  Is there fuel pressure?  

 

not sure, the car is currently still on a factory fuel pressure regulator so I currently have no way of monitoring fuel pressure but it would seem odd cause as stated I can keep it running if I apply some throttle for a few seconds. Is there a way to increase or decrease the time it takes for the ecu to pick up the cam angle sensors signal? maybe what is happening is it has not got synced with the sensor yet and needs more time to find it? I had a similar issue like this while using an old aem ecu where it wouldnt sync to the cam sensor fast enough and was a known issue with the old v1 aem on these cars. 

 

Edit* Just noticed in my tune file the IAT fuel correction was enabled, when I did these tests the car was already warmed up from me driving home using the modded factory ecu, so with the iat temps being over 180F its pulling 3 points of fuel out if im reading that chart right, would that be enough to cause the issue and should I disable that until the idle tune is finished and working properly? 

 

[Adamw]

11 hours ago, 2.0L_turbo said:

maybe what is happening is it has not got synced with the sensor yet and needs more time to find it? I had a similar issue like this while using an old aem ecu where it wouldnt sync to the cam sensor fast enough and was a known issue with the old v1 aem on these cars. 

It will not even attempt to run until it is synced. This should happen within 1 crank revolution for the evo trigger system.

 

11 hours ago, 2.0L_turbo said:

Edit* Just noticed in my tune file the IAT fuel correction was enabled, when I did these tests the car was already warmed up from me driving home using the modded factory ecu, so with the iat temps being over 180F its pulling 3 points of fuel out if im reading that chart right, would that be enough to cause the issue and should I disable that until the idle tune is finished and working properly? 

If changing the master fuel from 15 to 25 didnt make much difference (ie you are changing fuel volume by more than 50%) then I dont think the IAT trim is a big problem.    

Can you give us a log of it running longer with the throttle open or whatever.   Do you have ECU hold power wired so that the stepper motor is resetting at key off?

[2.0L_turbo]

1 hour ago, Adamw said:

Can you give us a log of it running longer with the throttle open or whatever.   Do you have ECU hold power wired so that the stepper motor is resetting at key off?

I can get you a log in about 5 hours time I'm just at work at the moment, and I have my relay wired in like this to activate the MPI relay as per your request from my harness adapter thread. 

 

[2.0L_turbo]

 

while out testing the car today I noticed the relay is shutting off and right after the car goes lean so I believe that is the issue here but how can I fix that?

[2.0L_turbo]

Solved it!

 

I figured out my problem, so with the way our relay was wired it would pull pins 63 and 66 to ground which is right, but what we missed is that once the engine is spinning on the stock ecu it also pulls pin 56 to ground as well and this keeps the fuel pump running. How I tested this was I temporary grounded out pin 7 on the MPI relay which leads to pin 56 on the stock ecu and then fired the car up with the link and she kept running for the first time. So I think all I need to do now is add pin 56 to 63 and 66 and we will be set.i will also add this to the adapter harness thread incase others try and copy it. I can able to now set the master fuel to 20. I now am facing a weird wideband issue but will do some testing on then and post if needed.

 

Edit* ok I realized a safety issue with wiring it how I described above, the proper way to do this would to be using another spare input and using it for fuel pump relay control and setting that to pull low after the car is running this makes it so that the fuel is not pumping as soon as you turn the key to the on position and continue to pump after the initial prime of the system. So what I will be doing is using another one of my outputs for coils likely B11 or 12 and setting it as followed 

 

pump control method standard

fuel pump relay output ign 6 or 7

aux ign test off

aux ign active state low

prime time 3 seconds

 

hope this helps!