Siggy

I have only just start logging and burning, using TCat and Datamaster 32x32. ECM 165, bin ACXS 32. I have removed AIR and EGR, burned my frist Eprom and set the fans to switch at 84C (on) and 78C (off) using 80C thermostat, I also reset the converter lockup to 35mph. Prior to this I had been using a adjustable thermo switch to control both fans, standard and the AC fan. I had isolated the ECM relay control wire when installing the thermo switch. Now that I can control the fans with a Eprom change I would like to remove the aftermarket switch and use the stock ECM control system.
Problem; I wired a small 12vdc light between the ECM control wire (DK Grn/Wh) and 12vdc and then logged the following; Cold start the light came on with engine running, Statis bit data showed "Fan PID"=1, "Fan Reqst"=0. After reaching a engine temp of 84C the "Fan Reqst"=1.
I.m not sure what Fan PID means?, and why does the light not cycle with the Eprom data?
It seems that the Fan Reqst bit cycles with the Eprom data but the control wire (light) does not cycle?

Sorry for this long description which no doubt has a short answer...help someone please.

RBob

iTrader: (1)

In the BUA code (32) the Fan PID status is set by the IAC routine. It is used to disable the fan. Having it set to 1 enables the fan control. As for why the output isn't changing I would double check the pin you are using.

Can also force the fan on at key-on, engine-off by shorting A & B together on the ALDL connector.

RBob.

Siggy

RBob, thanks for the info.
I did buzz the wire back to the ECM, I did not check the ECM pin ID but I found only two wires that matched the wire color code and one did check good, maybe Murphy Law?.
I also see that most of the 32 bins I read including my installed bin AXCS 32 have a ECM switch table setting (CATS 32x32) labelled "Normally open fan request", this was not enabled on any of these bins. I assume that this setting allows you to reverse the output logic state, normal being 1=enable and when selected would give 1=disable? In any case this would not help as the output never did change state during engine warm up from 18C to 90C.
I did have an engine fire with wire damage a few months back, guess I better confirm that I have the correct wire and ECM output pin.

Siggy

RBob....latest.

I traced it all back to the ECM....I found a 165 ECM plug pinout at Chevythunder (nice place) and learned that some of the aftermarket repair manual electricals are less then perfect, for my 165 the pins go to C1 and C11 and tested good.
Bad news is that looking further into the ECM, cover off my surge surpressor was toasty and had a hole in it....Power diodes also looked a bit sad. Decided that it may be time to look for a spare 165 before I get carried away with a solder iron.
I am surprised that the IROC runs so well....?

WHERE DO i LOOK FOR A SPARE 1227165 ECM, EBAY????

Siggy

RBOB...IAC routine?...I thought about that and I.m not sure what is meant by IAC routine, does IAC refer to idle air control?
In my effort to retain fan control by the ECM (1227165, $32b) I am finding conflicting infomation and unexpected output from the ECM.
My wiring appears (wire buzz with ECM unplugged) to supports engine fan at ECM pin C1, AC fan at D11.
I just replaced my ECM with a GM rebuild, but with the Eprom set for 184F (on) and 178F (off) for both fans the logic state is 0 (No Gnd) ignition on however after engine start and right up to 190F logic state is 1 (Gnd).
Am I missing something?

RBob

iTrader: (1)

Yes, IAC is idle air control. This is the logic/mechanics that control the engine idle speed. Have you tried key-on, engine-off and shorting A & B (on ALDL connector) together? That should force the fan on.

RBob.

Siggy

RBOB...question.

I'm expecting the coolant fan to turn on only when coolant temp reaches the Eprom fan on setting, is this correct? Or is the fan also controlled by other engine conditions?
I have sorted the wiring to stock but retain a manual switch on the AC fan circuit, the AC fan circuit provides a logic 12vdc to ECM INPUT pin D11 with all switches off, Coolant fan has single wire to coolant fan relay and ECM OUTPUT pin C1...at startup (engine run) pin C1 logic changes to Gnd (fan on) even though Eprom has (fan on) data of 185F and engine coolant is 82F?
I'm thinking that the ECM may request (fan on) if VSS = O mph? I will log more data but thought that knowing the intended program logic would help.