Ronny

iTrader: (1)

I have a stock 1984 Vette harness with an EBL'd 8746. I had the ECU HAM'd or modified to accept the stock car harness. Speedtronics provide unused pin #21 for lead to IAT sensor in HAM board. I tried two different new sensors(92 Camaro) and it is a no go. I get voltage(5V) at the sensor lead but no activity at Whats UP log.

The bits are properly set in .bin.

It is grounded to same as TPS and IAC are grounded.

What could be possible issues?

This is what RBob stated last year:

" Actually, the sensor doesn't have a polarity. The stock setup has the yellow wire going to the ECM, with the black wire going to ground. With the sensor unplugged and key-on, engine-off, the yellow wire (ECM input) should read 5 volts. The other wire should read ground (0 volts)."

RBob

iTrader: (1)

There are a couple of checks you can do. First, does your version of the WUD have a DIAG display? It will be one of the main displays as shown on the menu bar (WUD, TRIP, VE, SPK, DIAG). If not PM an email address and I'll send you the latest WUD that has that. IIRC you should have a version that has the diag display.

The difference is that the diag display shows the raw sensor values. Instead of the defaulted values on the other displays.

If you happen to have a 1K ohm (1,000 ohms) resistor around (1/4W, 1/2W, 1W, watts doesn't matter) we can make a quick test. Unplug the connector from the IAT sensor. Key-on, engine-off, probing the connector should show 5 volts (as you have done). Now, plug the leads of the 1K resistor into the connector. Measure the voltage across the leads. It should now be 2.5 volts.

Backing up a little. With the connector unplugged the WUD diag screen should show 5 volts for the IAT sensor. Then, with the 1K resistor in place it should show 2.5 volts (or close to it). If you don't have a resistor try using the IAT sensor. The diag display should show a drop in voltage with it plugged in.

If the voltage on the DVM at the connector doesn't go to 2.5 volts with the 1K resistor, then it is most likely on the wrong ECM pin.

If the voltage does change to 2.5 volts, but, the ECM diag display still shows 5 volts. Then it is either the wrong ECM pin or the ECM is bad (that ADC channel is f00-bar) or the connection is bad.

RBob.

Ronny

iTrader: (1)

Thank you RBob for the update. Version 2.1g.

Changed the .bin and enabled IAT by setting the flag in IAT21 and IAT25. Used the EBL.bin values for Blend. For reasons I do not understand the Prominator would not upload on first attempt. Failure. Second attempt it did UL successfully but the CE light came on and it apparently was running on limp. All three flags were set for IAT MALF.

I did datalog event for a few seconds. Reloaded a non IAT bin and Prominator successfully loaded. Now in logs I did not see a Volt read in Diagnosis? Just temp and counts. What are IAT counts? says zero Cnt's. Analysis just shows temp at 104F. I will verify the 5V at ECU tonight that I saw last season.

edit: A non IAT .bin uploaded successfully. First of 3 MALF flags was set but faint in color? Previously no IAT MALF flags ever on non IAT.bin.

RBob

iTrader: (1)

The Cnt's in the Diag display are the ADC counts. As you noted the IAT & CTS don't show the voltage, my mistake. However, with the IAT showing 0 Cnt's that is 0 volts on the IAT input.

So either the ECM IAT input is grounded, or the ECM is bad.

The Cnt's range is from 0 through 255. With 255 being 5 volts in. Which is what should be showing when there is no IAT connected. For 2.5 Volts (such as with the resistor) the Cnt's will be around 128.

Setting the flags IAT21 and IAT25 are what is allowing the MALF to appear. Unsetting those flags disables the IAT MALF's.

RBob.

Ronny

iTrader: (1)

The lead from the ECU was tested to be 5 volts. That was last fall 2007. Assuming that the lead is at correct position in harness(black 21) that lead should register at 5V with multimeter and would that not indicate the ECU is functional for IAT?

I contacted Speedtronics and thet asked that I contact you to see if the EBL is using a different pin? 8746 has IAT so I would assume EBL will not change the pin position and it too is pin #21? Now I am using a push fit connector temporarily as I was uncertain if there was polarity. I understand there is none.

I will also buy a 1K resister to wire in place of IAT sensor.

This is what thieitr website states. Not the comment for "air". I do not have a functional air pump system.

"1228746 IAT sensor:
If the Module is to be used with a 1228746 ECM, then an Intake Air Temperature Sensor (IAT) will need to be installed. There are two options available for getting the signal from the IAT sensor to the ECM:

1) An extra dedicated wire may be added to an unused pin on the ECM connectors (Black pin 21), routed through the firewall grommet, and connected to the IAT sensor. If so requested a connector terminal with a few inches of wire will be provided with the Module. The user must insert the terminal into the black ECM connector pin 21 and splice a length of 18 gauge wire (not provided) long enough to route through the firewall grommet into the engine compartment to the user-installed IAT sensor. The ONLY acceptable method for splicing these wires together is with solder and heat shrink tubing!
2) If the AIR switch is not being used, then the IAT sensor signal may be connected to the AIR SWITCH wire (Black pin 14). "

Now I am wondering if I have the lead on wrong harness connector? The other also has a 21 pin position. I will need to pull the ECU down and reapproach this. I wiill check # on other harness connector(AC clutch). As well as pin 14 per the comment.

RBob

iTrader: (1)

With the stock ECM connectors the IAT input is pin C12. It doesn't matter which base ECM is used, they are all the same ('7747, '8746, '6299, '8063, 4288, etc.). The IAT input on the stock connector is pin C12.

From what you posted about the HAM board it sounds like the pin used can be strap selected. For other readers note that the HAM bord provides edge card connection for the stock x-fire harness.

If you want, remove the ECM from the car and pull the top cover. The HAM is marked along the rows of pins where it is soldered into the ECM. Find C12 and then find which edge card connection pin it is attached to.

RBob.

Cartrax

Waking an old thread... Wondering how all this played out for you, Ronny. Which connection did you finally use?

Ronny

iTrader: (1)

I Believe it was 21. I recall sending the ECU back to RBob and he marked on the pin board where I should place the lead into the EBL/ECU. It, the EBL has worked flawlessly for past many years. But my ECU uses a HAM board connection since my 1984 Vette has the original wire harness. I think the designer of that board had a couple additional unused pin locations that RBob added the IAT input to one of. On RBobs site it shows the location at C12 so that may be correct for you. By coincidence today I pulled the IAT sensor which is threaded into my tubing between the blower hat and the KN cone filter. I went to a larger diameter tubing and KN cone filter inlet from 3 inch to 4 inch. My 396 stroker needed more flow capacity. I suspect it is 450 hp at the motor.

Cartrax

Nice. Thanks for the reply. Mine is running the best ever but I'm still trying to work out a lean spike (new post on this) then get the tune down better. My calculated HP now according to 0-60 times is well below where it should be.