I have been having TPS issues with my car so we hooked up a scan tool but it never gets a signal from the ECM. What would cause this. We have tried two different scanners and the ECM is a brand new AC delco.
thanks in advance.

 

any ideas anyone?

 

You did say anyone, so its your own fault

How does it run?

I ended up in similar situations but it was running funky, ECM would give no codes by flashing SES light or with ALDL on my laptop.

Ended up being a bad ECM the sensus was, when ya can't get any codes anymore and it runs bad......

New ECM fixed that but now I got chip problems.

Wanted Prom & memcal for 86 2.8 T5 MPFI 7032 ECM

 

The idle kinda searches around 800-1500 and sometimes stays at 1500. I can get codes to come up with the aldl through the SES light but the scanner won't even communicate with the ECM.

 

i had that problem. i was using a snap on scanner and it wouldnt do anything. luckily i work at a gm dealer and i used a tech 1 and it communicated no problem. though you could check your pins in your aldl and your scanner to ensure contact. you can teat and adjust your tps with a volt meter if you have no luck with a scanner. it should be at .5 volts closed throttle and 5 volts at wot. doesnt have to be exact

 

we tried a tech1 and tech2 scanner and neither worked. I have adjusted the TPS with a volt meter multiple times. the volt changes randomly like there is a short in the wire somewhere. not sure why the scanners won't work though.

 

i had a buick park ave that did that. i would adjust the tps, tighten the screws, then bump the throttle and it would be all messed up. it ended up being the tps bad. that communication prob. does sound goofy though, you could check to make sure you at least have a power or ground in the terminals of your aldl. the two pins may be ok to flash the light but you may have a broken wire or blown fuse to power up a scanner in another pin

 

If you are using a scanner that is only for OBD-II ecm's then it will not scan. All third gens didn't have this computer since it was around 96 when they came out. So that should solve you issue with the scanner.

 

no it shouldn't since a tech 1 is an obd 1 scanner and a tech 2 will still do obd 1 functions.

 

what wires should i check that go from ecm to aldl?

 

I will ask does your cigarette lighter work? Is that fuse blown?
I know on the GM trucks if the cig fuse is blown or the socket
is bad a scanner will not/cannot communicate with the PCM.

 

yes it does work and there are no blown fuses. thanks any other ideas?

 

Gotta chime in on this, I am having a similar problem, cannot get my ecm to respond to an AutoXray with the ODB1 connector.

 

OK so i found the wire diagram for the ecm and there is a orange and a blac/white that go from aldl to the ECM. The orange wire has continuity from aldl to ECM but the black/white wire does not. any ideas?

 

The black with white stripe wire goes to ground. Usually tied under the dash. This is from pin A of the ALDL connector.

RBob.

 

yes but it goes from pin A to the ECM. it's only a ground for the ECM?

 

Rob, just tried using a Max 232 aldl cable this time as opposed to the two transistor circuit. Still cannot communicate with my ecm. Like i said , i tried Datamaster, efi live, tunerpro, Freescan. I turn the key to the on position and do not get an SES light blink, I just turn the key on and always get a solid light. Any ideas?

 

Ok, I am getting a blink now when i turn the key. Still no connection through my laptop though.

 

UPDATE! It was a bad ecm not giving me 5v out of pin M on ALDL.

 

ALDL only goes up to pin L. It is a 12 pin connector; that only goes up to pin L.

 

Any your point for waking the dead ?

 

Why yes there was a point. I am working with an Actron 9690 scanner that is supposed to read out PIDs as well as codes from my 86 trans am. Since the scanner cries "error" and asks me to cycle the ignition key, but doesn't help, I thought I would come here to look for a thread. It all made sense until the Pin M comment at the end, which doesn't make sense since there is no pin M on the ALDL connector.
I was checking continuity on the cables that came with the scanner, specifically the OBD1 GM cable, and the 15 pin extension (6") to be sure it wasn't their fault. The cable is fine, although it only uses the ground pin A, the diagnostic Pin B, and the serial data Pin E. That should be sufficient if the software expects only those pins for data link communication.
This was the closest thread to my question and I was curious if the last comment about a pin M giving a 5v out pin M(sic) was a mistake. The unit gets power from a cig lighter, or back-up batteries in the unit for memory saves. I was hoping maybe the mentioned 5v from the ECM would be of some help, or at least another clue to track down.
Anyway, all searches and comments online are turning out to be negative when it comes to these dual purpose scanners supporting OBD1 with any reliability concerning "most" popular domestic cars. I did find one person commenting that he made it work with his 88 Camaro, although he got the "cycle you ignition key" request once in awhile, but was able to get data to flow, but not always. This encouraged me that maybe it will work, if I can only figure out what it tripping up the scanner's data collection. Mine looks like it is collecting data, the flashes a bit like it was going to display it, but then the error message stomps on it at the last second.
I know it's an old thread, but was hoping there would be more information now.

 

 

I believe the 1227165 sends data out E of the aldl when 10k is put across a-b
the 1227730 uses M and no resistor
look into tuner pro rt and a moates.net xtreme aldl cable or older snap on mt2500 or otc pathfinder. Not a fan of actron stuff

 

Ah, thanks for the pin-out. Plum forgot they do that with connectors (like, what happened to L?).
I plan to call these guys, and if lucky get to talk to an a tech that knows what their hardware/software is doing, handshaking, updates etc. Sure a lot of vehicle sound like they won't talk with this thing. Came with good recommendations, but realize now that it may be more sales pitch than reliable across (old) platforms. Specs looked good.
More of the old "large print giveth, and the small print taketh away.
I had that same feeling about them too, but worse luck with another, so this is the one I got. Works nicely with a 2010 HHR I tried it on. OBD2 tool, good. 320 some odd parameters poured out.
I'll look into the other suggestions, thanks. Funny, search engines only find what they want, cuz I was looking for more, and it just kept giving me 3 main ones, and simple readers. Guess those older manufactures timed out with the demand for OBD1 devices
I'm new here, I'll try to start a new thread if you think that's a better idea. For now, I have some research to do.

 

Support for the ALDL stuff on modern scan tools is spotty at BEST. I have a $14,000 Snap-On Zeus and a couple days ago I used it on a 93 LT1 Camaro. The RPM readout was 25% high. Confirmed this with not only the vehicle's tach, but also with TunerPro and I even used my Picoscope to get the optispark waveform and calculated the engine RPM from the waveform of the low resolution sensor. The scan tool's translation read out 2600 RPM when the engine was only at 2000. That's right - my MY $14,0000 SCAN TOOL is just flat out wrong with something as simple as RPM. Go figure. I want to throw that thing at my tool truck driver.

My suggestion is to get an ALDL to USB and use TunerPro. It's not the best solution either since it's open source and that comes with it's own issues but at least if you *have* to you can go through the HAC of the BIN and find the address of some data you want and stick it into the ADX.

As to the lack of an L - almost certainly it was skipped on purpose because it's too easy to mistake it for an I. Which - oddly enough - doesn't seem to be used either. My guess is the ALDL pinout and connector was decided upon before they had ironed out which pins and how many they were going to use. Also they left extra pins for future expansion which never happened when the government stepped in with OBD-II protocol.

GD

 

I recently replaced the plugs wires cap and rotor button with the fuel filter. It’s still starts hard and my obd won’t respond for the most part it runs well but at idle acts bogged down at times but straightens back out usually stays around 1000 to 1200 rpms. When I start the car no lights come on at all like usual when you first start only the infl rest light comes on and goes off all gauges seem to work fine. At times it will kinda pulsate in gear while driving at certain speeds. What could be causing this

 

Not sure about the lights on your console, as I don't have airbags in my 86. I think my comm problem has more to do with signal strength or wave-shape or handshaking than with the scanner. I haven't been able to get a scope on it yet to figure that out. I did get a replacement scanner, fibbed that it was an 87 Camaro instead of an 86 T/A, and it worked for PIDs for awhile. Then it quit next time I used it.

As for your stumble at idle, I can relate. Mine starts, stumbles, recovers then idles normally adjusting while waiting for closed loop after warm-up when the three items; CTS, O2 sensor and elapsed time are satisfied. Mine goes in and out of closed loop. It only stumbles at cold start first try. Cold start sensor was replaced long ago, and I thought I fixed that issue, (9th injector).

Then I saw in the data that a "lean condition" exists. This would mean the O2 sensor is struggling with the extra 02 that is present. When it goes into closed loop, ECM decides to add more fuel. When back to open loop, it just sucks gas as it ignores stoich calculations and is not going for mileage optimization. Either way, sucks gas.

I kept looking for a vacuum leak, trying to get back to basics as full tune-up did not help much. I finally found the probable cause. After the last session trying to read codes, and failing, I watched a now familiar pattern of getting up to temp (very slowly) then oscillating between 230 degrees and back to 210 as fan cycled on and off (as it should). I had recently swapped a stuck-open thermostat that was causing a very slow warm-up time. I think it was damaged by bad radiator cap that kept the overflow from working correctly, and caused leakage at the thermostat bulb.

The next day, cold, I found a puddle of water at intake manifold to head area. This was two cylinders or so away from thermostat area which was now completely dry and normal.
I'm pretty sure that is my vacuum leak. The engine stumbles, overcomes this leak with idle adjustments, then is able to warm up and runs better, but misses and has been getting rougher. It gets hot because of the lean condition, cools with fan, and repeats. All the while going open/closed/open loop I suspect. Can't be sure, cuz I can't get scanner to work to check it.

Runs well above idle, but sucks gas, and pings under hard acceleration, but good power. It also fails DEQ with excessive HC, but normal C0 and normal NOX levels.

Full tune; plug wires, rotor, cap, fuel filter, and finally plugs. New valve cover gaskets and PCV grommets and PCV.
EGR is new and works with vac applied, and temp sensor that goes with it is new.
Plugs had low mileage, and all looked identical but gummy. Not oil fouled. No dead cylinders. Power braking caused no shudders.

I'll change those intake gaskets, upper and lower when I get a round-tuit and a hernia surgery I need after working on this problem for months.

Since I found the leak, and it involves water, I'm not going to start the car again till it is sorted out.

I hope you see a tid-bit or two here that might help your search. Other peoples stories often lead me to see something new. I sure learn a lot when things break in "interesting" ways.

 

I like waking the dead...ever wonder why that it skips to "M"??? In alpha-numeric, "i" and "L" as well as "O" and "0" can be mistaken for each other so to eliminate this confusion, they omit it.

Edit: Lol...another thread about casting codes that I just read dis-proves this as the engine time stamping uses I and L.