IQ3 wiring help

#1

I’m wiring up my new iq3 logger dash along with stripping out all the unnecessary wiring from my harness (active check system and central locks etc). My brother is probably sick of me calling him to ask what every wire is, plus he is color-blind. I haven’t bought any vnet sensors just the 4 sensor module. I was thinking op, coolant temp, TPS and fuel level for now.

-Can I just tee the tach wire for the iq3 into one of the wires in the ECU harness, and which wire would that be? I still have most of the wires to the instrument cluster but I assume that is an analog signal?
-It says that linear motion sensors have to be calibrated. How am I supposed to calibrate the fuel level sensor?
-Can I use the wires that went to the instrument cluster for the op and coolant temp and which wires are they?

#2

Well I guess my brother is getting a lot of calls today. Maybe when I get back from buying the programing buttons and warning light someone will have responded.

#3

Most of what you want is present at the connectors that went to the cluster.

C1 pin 7 (Black) is the tach signal from the DME or you can use the wire off pin 6 of the DME connector.

C1 pin 26 (Brown/Violet) is coolant temp sensor

C2 pin 4 (Brown/Green) is the fuel gage sensor

For oil pressure you’ll have to install a sensor as all the car came with is a pressure switch for low oil pressure warning. A VDO 0-100psi (0-180ohm) sensor, like for an oil pressure gage, will do the job (http://www.egauges.com/ is a good source).

You will have to enter calibration data for these sensors. I use 180ohm pull-up resistors connected between +5 and the sensor input in the USM. You can work directly with the sensor resistance via a Custom Cal Table. Input the value of the pull-up resistor and the sensor’s data and the S/W will calculate the rest.

The data for the fuel gage depends on what tank the car has. Early production (up to 8/87) has a 55L tank with a single level sensor and late production has a 63L tank with two level sensors. The early tank will be 60ohms when empty and 0ohms at full (14.5gal). The late tank will be 120ohms empty and 0ohms full (16.5gal)

If you use a 0-100psi oil pressure sensor 0ohms is 0psi and 180ohms is 100psi.

The temp sensor is non-linear. I calibrated three sensors and averaged the results to get a representative curve. The data (resistance/temp)is:

4619.56 / 0
3557.15 / 8.12
2763.62 / 16.25
2165.39 / 24.38
1710.37 / 32.50
1361.36 / 40.62
1091.50 / 48.75
881.23 / 56.88
716.21 / 65.00
585.78 / 73.12
482.00 / 81.25
398.91 / 89.38
331.96 / 97.50
277.72 / 105.62
233.51 / 113.75
197.30 / 121.88
167.48 / 130.00
142.80 / 138.12
122.28 / 146.25
105.13 / 154.38
90.75 / 162.50
78.64 / 170.62
68.39 / 178.75
59.68 / 186.88
52.26 / 195.00
45.91 / 203.12
40.46 / 211.25
35.77 / 219.38
31.77 / 227.50
28.19 / 235.62
25.13 / 243.75
22.46 / 251.88
20.13 / 260.00

#4

thanks. So the signal wire goes in the signal hole on the usm and a 180ohm resistor goes between the +5 and the signal hole because the sensor isn’t powered by the usm? The ground goes to the nearest body ground and the shield is not used?

#5

I got some 220 ohm resistors. Will they work?

#6

Just finished soldering the main harness and putting the coolant temp and fuel level in USM. Is this right?

#7

The car won’t crank now. I think its because I cut the wire to my clutch switch since I was also removing the cruise control wiring.

#8

ok it was that and the fact that I unplugged the circular connector to the engine harness so I could have more room in the fuse box. My brother stopped answering his phone now.

#9

clutch switch?

#10

Most manual cars won’t crank unless the clutch is depressed. Mine is a white micro-switch with a red plunger above the clutch pedal. It also turns off your cruise control when you press the clutch in.

#11

The switch that tells the ECU you have the clutch pedal in and to allow you to start the motor.

EDIT: A little late.

#12

Wow someone finally says something when its captain obvious time.

#13

doh, i know what it is, my e39 has it but it’s not present in any e30 i’ve ever owned… and i’ve had a few…

#14

That is kind of weird. There is one shown in this E30 pedals image. I have never checked my car for one:

#15

Well the dash and programming buttons work and amazingly it picks up 9 satelites inside the garage with the doors closed. I still need help with this V-net module thing. Can I get a yay or nay from an electrical engineer on here.

#16

interesting fact: ground to the steering column is provided by the turn signal relay wires. ask me how I know this.

#17

I wanted to log throttle position and eventually brake pressure. I don’t see anything in the bentley about an actual tps, just full throttle and idle. Does the ECU not get a throttle % signal.

#18

turbo329is wrote:

Correct. No linear TPS. You’ll have to buy a string potentiometer. For the brake, you can tap into the 3rd brake light for a binary signal. Otherwise, you’ll need to inline a brake pressure to get real data.

I got both sensors from gormans.

#19

Whats the max psi for the brake pressure?

#20

turbo329is wrote:

MSI 0-2000 PSI Brake Pressure Sensor

I have been pretty lazy and haven’t gotten around to installing the sensor. I might be interested in selling it. I paid around $140 shipped.