CLT reading problem- doesnt read at all

[steveep82]

Hi all, im i the process of putting ms2 v3.01 board, main board is v3.0, in my toyota starlet ep82 (4efte engine) Its all in, the engine starts and runs, i get readings from everything except the CLT- coolant temp sensor, The sensor is now wired direct to the megasquirt loom with the earthing point the same as the sensor grounds for megasquirt. Ive checked for continuity on both earth and to the pin on the db37 on the loom and all is well there it seems. Also checked the resistors are 2.49ks which they are. ive checked for continutity between the pins on the db37 as well on the ecu and that seems fine, giving a reading of 3.09. Ive tried two different coolant temp sensors and both give no reading, all that happens is the temp starts at about 350 degrees and then falls rapidly before starting to fall slower from 120 degrees the settleng at roughly 70degrees. Im stuck! any ideas? ive used the following resistor settings when calibrating the sensor in megatune:

0 degrees celcius- 15600 ohms
18- 2050 ohms
100- 184 ohms

Left the bias resistor as it was.

[Matt Cramer]

How does the CLT reading behave when you test the MegaSquirt on a Stimulator?

[steveep82]

I dont have the stimulator unfortunately, i bought the ecu as ms1 and then bought the ms2 daughterboard to upgrade it but it was all ready assembled. any ideas? not looked at it for a couple of days due to other work but would like to get it resolved

[Matt Cramer]

Measure the voltage on the CLT input pin on the 40 pin header and see what the voltage is there.

[steveep82]

Ok, i did that, im getting 4.85v when the sensor is unplugged totally, if its plugged in and at about 20 degrees celcius its reading 2.5v and at about 40 degrees c its about 1.35v, this sounds about right too me, do i have a software problem?

[Matt Cramer]

Sounds like it... try reloading the firmware.

[steveep82]

Ok, so we tried reloading the firmware today, no difference, we decided to try going back to the ms1 chip originally insalled into the ecu when i bought it, still no difference, does the same thing, temp starts high and then falls, no matter if the sensor is plugged in or not. Getting really stuck now! Going to try my ecu in my mates squirted car tomorrow, and see if it still does it, i guess if it does, then its a problem with the motherboard?

[Matt Cramer]

Sounds like you'll need to troubleshoot the CLT input circuit.



My guess is something's wrong with R8.

[steveep82]

Problem solved, a dry joint on r8, soldered it up and now the coolant temp is stable and correct Thanks very much for your help Matt, much apprieciated!