Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Link G4 x question

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads


Hi all,

I have a G4x ecu and trying to learn /map it. I have powered the car on using the ecu as had to swap the wiring from m52 to m50 and now want to connect temp sensor for water and oil to the ecu which is form prosport.

the gauge output using ohm so I bought an expansion connector and made the 8 pins which go to the connector. now my question is what is ground on the expansion loom as well as the 5v+?

I am trying to use temp 3 to read from the signal wire of the gauge and so far no luck.

Expansion loom will have a sensor ground on it as well. Typical sensor wiring is one wire to signal in, and the other to sensor ground. AN temp's have a 1K pull up already so no worries there.

I'm not fully sure what you're trying to do, is there a reason to not use the original coolant temp sensor wiring? If you're trying to read the oil temp or oil pressure gauge's signal you should use a AN volt with no pull up resistor. And really you should use a proper sensor and leave the gauge alone lol

Thanks, I am trying to read oil temp and oil pressure from the prosport premium I have, link to manual attached

I can’t really run another sensor as the slots for them are taken up by gauge sensors which connect to the filter head

I think output is ohm and way the sensors are wired they have a ground and signals at the sensor. I tap into signal wire and connect it to temp3 which didn’t work

i connected it to an volt 4 and set calibration table 2 to ohm and temperture and this seemed to work. I just need to find the ohm to temp values

i still don’t know use of ground and 5v+ on the expansion loom. Would you mind elaborating?




Your statement "I think output is ohm" indicates that you likely will benefit from expanding your knowledge of basic electrics. Please, I do not mean to discourage!

A good place to start could be:


Personally, I would rather have the ECU read the value from a sensor and use an analogue output to the external display unit.

From an outside point of view, a visit / call to one of the many very reputable LINK dealers might much more expedient for you.


thanks for the feedback, I am looking to learn EFI than paying someone . I live the journey and thinking once I get over this then can start looking into more cool stuff

Perhaps you consider a combination of learning by yourself in conjunction with someone savvy and hands on, to enable you to make progress with your projects without to much headache, money and time wasted needlessly?

Best of success to your endevaour.


Thanks, I use this forum as part of the journey as well as great course by Andre/HP academy

I should state I re read my post and what I meant was input is ohm. I use multimeter fair bit and know ohm vs voltage vs pressure etc all basic stuff so my bad there. still fair bit to learn.

one thing I am trying to understand is if the sensor is sending ohm as input then why link shows it as volt. this is all what I need to learn

The sensor is not sending Ohm.

Ohm cannot be sent, EVER!

Ohm is the measure of electrical resistance in a cirquit. Some ECU's will allow to enter this resistance value in calibration tables, some the resulting voltage from the voltage divider (pullup/ pulldown resistor, internally or externally) and the variable temperature sensor resistance.


Let me elaborate on what Dominque has said, ECU's cannot measure resistance directly. They can measure voltage, so we need a method to convert a change in resistance to a change in voltage and then calibrate in the ECU. We do this with pull up resistors, or fundamentally a voltage divider circuit. I recommend taking the Wiring fundamentals course and getting familiar with Ohm's law before learning about voltage dividing circuits as it wont make sense without that context.

I would also recommend finding someone local who's more knowledgeable and buy them dinner to pick their brain and ask questions.


I made a video covering wiring and setup of pull up resistors on ECUmaster, but the same fundamental's apply to Link or any other aftermarket ECU.

I see two paths to solving your issue without adding more senders, and both are a bit complex but I have done both successfully;

1: You can wire the gauge signal wires into AN volt inputs into the ECU. AN volt do not have pull up resistors (AN temp do and can't be disabled), but the Gauges will and having 2 pull up resistors will divide the circuit again and cause incorrect readings to both devices. Then you can use the gauges to figure out what voltage you see on the ecu corresponds to what temp and add that into the table. Without knowing what pull up value Prosport used inside the gauge there isn't really a way to calculate from the sender resistance.

2: You can wire in quality sensors with published data (Link, Bosch, AEM, etc etc shameless plug I sell them lol) to the ECU and use a PWM output from an Aux on the ECU to control the gauges. This will also require some calibrating and testing but is probably more accurate and reliable. Provided the frequency is set correctly on the output the gauges won't know the difference.

The Link expansion looms are colour coded and defined in their user manuals, but there are two variants and I don't know which you have. Typically there's a sensor ground, 5V, digital inputs, voltage inputs and temp inputs in the 8 wires.

Thank you both for your guidence and time taken to explain

having read the earlier comment, I remember the law of where one v=a by resistence( if i remember correctly) and resistance is something to be measured and volt is what is on the circuit

I best do some more research and the course .

i will post back if I have any other qs. Thanks again

I managed to get it to work and it is within 1-2 degree of the gauge

Oil temp connected to an volt 4 with 1k resistor ( the gauge may have that on) and an volt 5 to oil pressure.

table I received from prosport and used calc table 2 and 3

Me again:)

last time I spent time calibrating it and seemed ok but now off in the same range

From experience I know ( correct me if wrong) when you tap into a wire you could change/add its resistance hence on most modern cars you can tap into say indicator wire etc

now considering above, I checked whether when I tap into it, will the gauge reading change and it doesn’t

i created a calibration table based on link below which is the sensor with the gauge however values don’t match

i am now fed up and thinking screw this, I come up with some t function work and buy another sensor with data and also retain gauge one

i see the post from tyson and appreciate the input however I think if I buy a sensor and then aux out to gauge, will it work or not unsure.

I don’t know how gauge is setup / i guess the board is based on the sensor so prob won’t work with my aux to gauge

before I ditch this, does anyone know why values were within 2 psi and now it is like 20psi?


Ignore me, found it was ground issue. Here is my wiring and appreciate some advice

my gauges are wired to 12 v and ground( chassis) which feeds multiple gauges using 5amp fuse.

I have not fixed the ground wire to the chassis yet as had not time and it was secured by twisting it on another ground wire .

Now one of the gauges which is prosport wideband, gets 12v and ground from source above but has a control box which then feeds gauge and sensor power . The control box has 4 connectors which are, one for power , one to gauge, one to sensor and one output for ecu

now on output there is three wires which are ground, wideband and narrowband

i wired the wideband and ground in to expansion loom

now that is background, my issue was the ground which feeds all gauges had come off so all gauges were using the ecu ground through the control box and number were off

put the chasiss ground on and booM all worked

now i am curious and have following questions and appreciate any input.

should sensor use chassis ground or ecu?

can ecu ground be shared with multiple sensors? I would say yes

finally why when chassis ground was disconnected, all gauges worked through the control box . I disconnected the ground which goes to ecu and can see both afr and all gauges still worked fine

question is , why on output they also have a ground ?

see link to manual below which hopefully makes sense. also pic attached


Attached Files

Here is calibration data for anyone running into same issue

sensor part number PSSMOPS

Attached Files

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?