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2000 Buick Lesabre, 40 different codes... where do I start?

J_dude

J_dude

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So my Dad’s Buick has some issues...
Service engine soon light came on and she was running rough intermittently, plugged the code reader in and FORTY codes! Naturally.
Anyway, I’ve no idea where to begin.
Car is a year 2000 Lesabre with the 3800 v6 engine.
Not sure the best way to show you all what the codes are, I’ve got them all jotted down on a piece of paper but not the descriptions.

There’s a few MAF codes, some MAP codes, TPS and ECT. 10 codes related to Heated Oxygen Sensors, Fuel Trim Lean and Fuel Trim Rich on Bank 1, all 6 Injector Control Circuit codes, Misfire Detected, PCM Knock Sensor Circuit, CKP Sensor A Circuit. Cam position sensor, and then some EGR and EVAP codes, Vehicle Speed Sensor and Engine Oil Pressure sensor circuit low voltage...
Yikes
Let me know what you all think.
image.jpg
Thanks!
Jude
 
Load test battery as well. A brown out when cranking gets "interesting".

Clean ECM engine ground.

Look at voltage ECM is telling scanner. How close to battery voltage is it?

Possible ignition switch. Low voltage to ECM as above.

Next IF the codes return ... Keep in mind a short on a 5V sensor wire can take several sensors out.
 
WarWagon said:
Load test battery as well. A brown out when cranking gets "interesting".
Click to expand...
Yes it does, my friends 2015 GMC suv kind of a thing, whatever its called, had all kinds of codes popping.
He got the battery tested, bad battery even though it was still cranking and starting the enjun just fine.
New battreee and no more problems.
 
Bad power to the fuse block will cause much the same thing, too. Ex-gf had a '97 Sedan DeVille that did much the same thing. Be driving along and all of a sudden everything would just shut down/off - engine, accessories, everything - then mysteriously come back on a few seconds later. Damn scary in the middle of traffic let me tell you! Put a code reader on it and came up with dozens of codes covering just about every system in the car.

Did it to me one day while I was driving down Capitol Parkway at 45mph in heavy traffic and hit a pothole in the street and everything shut down! Instinctively I just took my left foot and pushed up against the fuse block up on the firewall under the dash, felt it move just a hair, and everything came back on and the car kept running!

Took it to my favorite (and only) mechanic who 1) diagnosed that the ECM was toasted from losing power then getting full voltage back multiple times and the car was running on default limp mode. 2) For some reason the power lead into the fuse block had loosened enough that it had arced at least once or more and the result was it was causing poor conductivity/open circuit (much like burned points on the old style distributors). So, he cleaned up and reinstalled the power lead using a star washer nut on the stud and torqued down good and ordered and installed a new ECM. Car ran great after that, she wound up getting rid of it a year later after a stupid accident on her part. Winter, parked on the street, the plow truck had left a 2' tall ridge of snow along side of it. She just partially dug out, figured she could "blast" out through the rest of it. So she blasted out of it - and across the street into the side of her neighbor's car! That's when she found out that most of the front end of her car was plastic - the fender, grille, grille surround, filler panel, etc. - and that it was damn expensive to fix!
 
Ok I finally got a minute to look at this car again. Cleaned up battery connections and tossed a known good battery in her, tried clearing codes but they come right back immediately... although I’m not certain the cheap code reader is capable of clearing them? It says “clearing successful” or whatever and then it goes back to all the codes again. I might go over the other main 12v and ground points and make sure they’re clean tomorrow.
 
Assuming the codes cleared this is a good thing. Means it's not intermittent.

Quick and dirty test:
Codes cleared with engine NOT running. Is the Misfire Detected code back? Yes = codes did not clear.

If the grounds and ignition voltage to ECM check out the next step is looking for a dead short on a sensor or wire to a or several sensors. Mice damage, minor road debris impact to harness, etc...
 
After talking to my friend Bob. After about a year with the new battery in his envoy, one code came back. Misfire on one of the cylinders, 5 i believe.
He went and got the battery tested, bad almost new battery. Carquest replaced the battery, cleared the code and it has been trouble free since then.
 
this does sound like a shorted 5 volt signal from one or more of the sensors. do like WW says looking for a misfire code after it is cleared. if no misfire code then start by disconnecting every sensor related to the codes shown. re-clear them, get you a multi-meter to read the 5 volt signal from an easy to get to sensor like the CTS or other. then with the key on, start re-connecting each sensor one by one watching the 5 volt reading on the meter. take note of the condition of each connector on the harness and on the sensors as you re-connect. when you see a drop in the 5 volt to anything below 3 or more, you may have found the guilty sensor or connector / harness area at fault.
 
Also pay special attention to any areas of the harness where an oil leak has saturated the harness, also if there are any areas near a heat source like the exhaust manifold. oxygen sensors shorted up in the harness can cause some weired issues. I have also seen the harness go bad that connects to the MAF too.
 
dbrannon79 said:
Also pay special attention to any areas of the harness where an oil leak has saturated the harness
Click to expand...

Adding too this: Oil is an INSULATOR. If it gets in the connector it can cause an open connection. Say the 89 Olds 3800 valve cover leaks oil into the knock sensor connector. Started out in the usual way but hard to find.

SES kept coming on with no codes and limp mode.

Ok after shop replaced failed ECM that couldn't remember...

Code saying ignition module timing failure and limp mode. After swapping the ignition modules out, ECM again, testing the harness for timing signal wires...

Finally, took all summer, the shop tracked it down to the oil leak on the knock sensor. The sensor and connector were deteriorated enough to let oil in... And that insulated the connection so the engine never could tell the ECM when it knocked. ECM would step timing to max advance. If it didn't get a "knock" it's primitive programming said ignition module failure. Not a Knock Sensor Deaf/INOP code...
 
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