94 Lesabre EST not toggling

A few times over the last couple of weeks, my Service Engine Soon light has been coming on. It only happens when I've been driving the car for a while--say around 25 miles at 65-70mph on the freeway. Using my Actron CP9145 scanner, I get a P0361 trouble code, "EST Not Toggling." (With this car, I know there's some question about ODB or ODBII implementation.)

When the Service Engine light comes on, it feels like the engine is running a little rougher and that there's a slight loss of power. When I stopped at a store today for a few minutes, I came back out, and the Service Engine light didn't come back on, making me wonder if it's heat-related.

I've read other posts related to this code where the advice was to replace the Crankshaft Position Sensor.

The car has ~125k. I bought it from my uncle when it had about 95k on it, and, among other things, I had to replace the ECM.

Other suggestions related to this trouble code were check the ignition module and coils. I'm actually a professional electronics tech, so I have all the equipment to check the electronics I need, including an oscilloscope. I just need to know what I'm looking for. Of course, what may make this difficult is that it's an intermittent problem. I know that some transformers can develop intermittent shorts that only occur when the transformer heats up.

Recommendations for how to proceed with this diagnosis?

Thanks!

Thats a code 1361, and more than most is one of 2 things... Either the ICM or the PCM..

When you replace the PCM what did you replace it with?

And the P0361 is actually 1361, the Actron does not always display it as a Manufacturer specific code...

The car is full on OBD1, but uses an OBD2 connector and OBD2 codes..

Thanks for the help!

When I replaced the PCM in 2004, I think I bought a replacement module at Advance Auto. I know I paid around $100 for it. Before replacing it, the car would run OK for a while and then suddenly start running rough. My brother and I drove it with the code scanner attached, and it spit out something like 20 error codes at once. We decided it was more likely that the module was bad as opposed to 20 things going wrong all at once.

I remember that I had to remove the PROM from the old module and install it in the new one.

I'm trying to think of the best way to distinguish a PCM problem from an ICM problem.

We have had a lot of lightning storms around here this summer. I wonder if there could have been a strike close enough to induce a voltage that damaged the PCM's processors.

I am not going to tell you to replace that PCM until you know its bad...

The 94-95 3800 PCM's are some of the worse in terms of failure that I have ever seen... I have seen the older 92-93 PCM's will 250,000 miles on them still going... Pretty much never seen a 94-95 PCM manage that..

On my 95 Bonneville I have been through a total of 5 PCMs in 184,000 Miles... Factory unit failed at 110,000... Code 1361... I too thought ICM... Swapped it out to have the same problem... I got an Advance PCM and problem solved... 1 year later it would do a random stall while driving and then poof back to life.... Once again Code 1361..... I got a junkyard unit and that lasted a while then I ended up with a start but no run condition... The ICM actually starts the car, the PCM is supposed to take over after 400 Rpms... Never happened... You could get it to start, but it wouldn't run good.... The next one did close to the same and only gave me a couple of months.. By this point I was tired of this junk and kept a spare in the trunk... The last one had an issue with the 4k Pulse used by some of the cars electronics, like the Variable Effort steering, Cruise control I think... among a few other... And it sent the dash module into a dinging frenzy as it lost the 4k pulse...

We finally got pissed and updated the 95 Bonneville to a 97 PCM and Wiring Harness( PITA, but cool to be able to tune it at will with the Lap Top )

I also have a 95 Transport, it too did the 1361... I popped another PCM in it and later had idling issues... Never did get that figured out... We rewired it to also accept a 97 PCM for tuning reasons... Funny even with a .517 cam it idled better than it ever did before...LOL

It has to be either the ICM or PCM.... Would you happen to have another 3800 in the household? All of the ICM's and coils on the 3800's are the same from 1993 to the end of production..

I replaced the PCM this morning with a $110 remanufactured OEM unit from Advance Auto, and, so far, the new one is working fine and has spat out no error codes.

As an additional bonus, my cruise control, which hadn't been working for a while (Servo Position Sensor Error)--and which I'd been trying to diagnose-- came back online. I tested the Servo Sensor with an ohmmeter from the connector, and it tested good. I even swapped the old PCM back in to see if simply moving the connectors had restored cruise control, but it appears that the problem was in the old PCM.

I haven't had a chance yet to do an extended highway drive to thoroughly test it yet, but I'll report back.

Yeah, Don (Jrs3800) is right, the 94-95 PCM's are prone to failure. When they go bad, all kinds of (what you would think) unrelated problems appear, including trans shift functions & lack of cruise control. Been there, done that! You should be good to go for awhile (until it fails again). I hope Advanced offers a lifetime warranty, like O'Reilly does.

Yes this failure is far too common on the 94-95 3800 Vans, C Bodies and H Bodies... I have seen it a battery of time and not only with my car and van..

The last one was that a Buddy of mine sold his 94 SSE Bonneville... The people owned the car for a year and one day out of the Blue called him up and said they were having problems... Car would run but you couldn't drive it.. And it had a series Of codes... My buddy asked me what I thought... I told him to call the guy and tell him to replace the PCM as it bit the dust..

Guy replaced the PCM and later called back stating that the car runs great...LOL

Let us know how the highway run goes..:)

The Lesabre made a 30 mile round trip on the highway today with no problem, so I think I'm good to go for a while. Thanks for saving me an unnecessary crankshaft position sensor replacement! I'm guessing that the computer module would heat up to a certain point and then start malfunctioning.

Now, if I can just figure out the remote door locks issue....

Start a new thread on the Door lock isues, and I'll see if I can help... PM me the link to your new thread when you get there...lol