slrvette

iTrader: (1)

Just a quick question. The MALF codes window.
Code is on the left then you have 3 boxes to the right. When a code pops up all three boxes turn red. But sometimes when there isn't a code .. the box furthest to the right may be red. Does each of these boxes mean something?

RBob

iTrader: (1)

Yes, the 1st column means that there is an immediate error. Which will sometimes blink as the ECM zeros and and re-tries to see if the error still exists.

The 2nd column means that a SES light is pending. If the error remains long enough the SES will be activated.

The 3rd column is a code that is stored in the ECM. This is retained at key-off. And can be read out via the ALDL or blinked out via the SES (short A&B, key-on, engine-off).

RBob.

slrvette

iTrader: (1)

Thanks, thats a nice easy to understand explaination.
The reason for the question is because I'm having a constant problem with a Code 23 (IAT Lo).
Replaced the sensor 3 times .. all ohm'd at 1.66 on the 20k scale
Each time I've had 5 volts on the harness.
I'm gonna try to change out the harness and am hoping its the connection between that and the sensor

Ronny

iTrader: (1)

Does IAT low mean the intake air temp is low or the voltage low?

RBob

iTrader: (1)

It is either the sensor or the circuit is open. IOW: unplug the sensor and an IAT low will occur.

RBob.

slrvette

iTrader: (1)

RBob, I can't remember the pin number on the black ecm connector that the IAT is. Can you refresh my memory? (misplaced my notes), thanks

RBob

iTrader: (1)

Black 21 is the common IAT pin input. Black 14 can also be used. Although IIRC there is a jumper involved if so.

Either way, on the ECM itself, the IAT input is C12. This is the pin that is between the HAM board and the ECM itself (the vertical posts). The HAM is marked for the A, B, C, D, 1... connector pin positions. Will need to pull the top cover to get to those.

RBob.

slrvette

iTrader: (1)

Looks like I'm gonna have to dig into the connections at the ecm or possibly the HAM board.

Still getting a pending code and the SES is turning on and off.
MAT is new
Harness that connects to it is new
5 volts at the connector, Resistance at sensor is 1.66

Since the code means "open circuit", does it sound like I'm going in the right direction?
thanks again


I removed the ecm and the wire going into black 21 seems fine and tested fine. Solder joint between HAM board and main board is solid as well.

What about trying to clean the edge card connections? If so what or how should I do it?

RBob

iTrader: (1)

Does the other wire to the sensor have a good ground?

For cleaning the edge card, some brakeKleen on a paper towel and wipe them.

RBob.

slrvette

iTrader: (1)

Per your instructions to clean the HAM board connections I did that. I also used a electronics cleaner on the plug connectors. Let those dry for a while.

My CTS and MAT share the same ground. I remove the butt connector in there and for now restriped the wires and used a wire nut.

Let the car warm up into closed loop, then took a short 2 mile ride. At this point I have no code... nor a pending code. So lets keep our fingers crossed that this is resolved. Thank you for your help.

slrvette

iTrader: (1)

Drove it an additional 15-20 miles and the code came back. Its intermitant. Aside from running a new wire out to it and giving it a new ground anymore ideas?

RBob

iTrader: (1)

Nope, it's real simple. The ECM provides a +5 volt signal via a pull-resistor (pin C12). The other side of the IAT sensor goes to engine block ground. Two wires, a connector, and a sensor. Nothing more to it.

RBob.

slrvette

iTrader: (1)

LOL.. thats what I thought too! Little did I know. Something is making and breaking. I may try a temporary wire and a direct ground to the block and see if that will solve this problem.
I have an extra voltage gauge I could also temporarily set up in the cockpit to see where the voltage is at when this happens. maybe it could help me tell if the voltage issue is at the ecm or further out near the sensor.
Can't let 5 volts beat me!

slrvette

iTrader: (1)

Back at this today.

Both the MAT and CTS are 2 wire sensors. 1 +5 volts and the other ground.

Presently both grounds are connected to the ground that goes back to the ecm. I have already confirmed that the ground is a solid connection all the way back.
Should I try connecting those to a block ground? I wouldn't think it would make a differance just trying to come up with a solution.

Any way to confirm that the ecm isn't have the interminate problem?