At first I thought the trans was slipping until I power braked it. At around 2500 rpm, the engine acts like it’s misfiring badly. At one point during hard acceleration, the SES light started flashing but abruptly stopped seconds later.
I have been putting E85 fuel 2.5 gal max) and then the rest with premium. I hope this isn’t a big no no and also causing the problem. Has a new fuel pump and filter. I will have the parts store hook up their DST and give a report.

Any suggestions (and criticism for the E85) welcome. Was running strong before this and would like to get it back to that.

Nothing against running ethanol past the normal 10% found in most gasoline but this this isn't a flex fuel car with a flex fuel sensor. Your pcm isn't going to know how to compensate correctly. The rubber, seals etc. in your fuel system also wasn't designed to handle higher ethanol content but many have gotten away with short term use.

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

Based on that, will stop putting the E85 2 1/2 gallons mix in it. Think that could be the cause. I just hope it isn’t something more serious.

Codes pulled: P0300 (stored) P0134 (stored) P0137 (stored) P0140 (stored/pending) P0452 (stored) P0135 (pending) P0138 (pending)
I hope this can give more clues as to what’s going on. I will swear off that e85 stuff too. Any/all help is appreciated.

Well… according to the code readings from Autozone, I think I’m going to need a complete wiring harness. The DSC said the ECM had no communication with the powertrain control module. I do t see how that’s possible because my transmission is shifting.
Anyhow… where on here or outside this site can I get a harness? And how much would it be?

I think you might want to go to another place for codes. There's no transmission or engine only computer, only a combined engine/trans Powertrain Control Module.

If you do need a harness, Andrew, Harofreak00 of Bonnevilles Unlimited is the way to go.

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

Where’s the primary harness coupler located? If it’s on the driver side near the transmission, I found a couple pins with oxidation. Possible cause?

UPDATE
I should have mentioned that the oxygen sensor is new. And I believe that what is happening under hard throttle is that it's a lean condition. Possibly due to the E85 fuel I have been feeding it and also that the injectors are suffering failure due to it as well.
The code pulled from the Autozone DSC are as follows
U1300 - Class 2 circuit short to ground
C1214 - Solenoid valve relay coil or contact circuit open
C1222 - Right front wheel speed sensor input signal = 0
C1225 - Left front excessive wheel speed sensor variation
C1232 - Left front wheel speed sensor circuit open or shorted
C1233 - Right front wheel speed sensor circuit open or shorted
C1238 - Right rear wheel speed sensor circuit open or shorted
C1245 - acceleration sensor output
C1248 - EBCM turned the red brake warning indicator on
C1276 - delivered torque signal circuit malfunction
C1284 - lateral accelerometer sensor bias malfunction
C1285 - lateral acceleration sensor circuit malfunction
C1285 - Steering sensor rate malfunction
C1288 - steering sensor circuit malfunction
C1295 - brake lamp switch circuit open
C1298 - class 2 serial data link malfunction
U1016 - no communication with power train control module
U1255 - Class 2 communications malfunction

So yeah..... car is a mess in a nutshell. Am a veteran on fixed income and I have absolutely no idea what to do here. To top it all off, I think my final drive is about to fail as well

First I would Delete ALL those codes and drive it again until it does what your are talking about and then re-read the codes. my gut (IF) and that's a BIG IF all those codes are legit...you have either a short to ground or short to power on the 5v reference circuit and or a short (maybe the two wires together even) on the Class 2 data circuit. Diagnosing this type of issue is a lot easier with an oscilloscope (Pico Scope, FLuke Scopemeter, MicSig ATO1104, etc.) I would recommend you watch some videos on youtube by "Scannerdanner" the guy is almost a "god" when it comes to troubleshooting electrical/electronic issues. Finding a competent Diagnostics guy is usually the hardest part and it isn't really something that can be done over the internet. I charge $75/hour doing diagnostic troubleshooting and that is cheap. You have to remember fixing electrical issues is normally the oposite of standard mechanic work...mechanic work...your mechanic says your water pump is leaking (easily observed), that will be $350 labor to replace it. Electrical you pay for the expertise to track down/locate the problem wire/connector/circuit etc. and a lot of the time the fix is cut bad wire out, solder in new wire, insulate & protect and done...cost of wire and solder etc...maybe $10, the $310 fee is the 4hrs ($300)it took to track down and (sometimes) get to the bad wire etc. and fix it ($10).

The primary harness runs from the PCM (which is located inside the air box, then out and off to the fuse/relay center then inside the car (not counting all the stuff that splits off under the hood from there).


I am an Engineering Lab Tech for my day job, but I work on vehicles on the weekends in my spare time. I spent almost a year off and on working on a guys jeep tracing and replacing bad electrical wires and connectors...his jeep would drive fine for 20-90 minutes then just die leaving him stranded on the side of the road for 15-20min. but it wasn't consistent...sometimes he would drive it for days/weeks with no issues in all types of weather....he replaced every sensor on the vehicle, some multiple times. it took using my Fluke Scopemeter and watching the 5V ref circuit to see what was dropping (when I could get it to do it for me) before I finally fixed all the issues it had.

In the end I had to replace one 30pin connector to the PCM (yes cut, strip, solder and heatshrink every wire) as well as rewire the entire 5v circuit...I narrowed the damage to a section of the harness behind the engine and it was easier to rewire it and cut the old circuit out of the harness than to tear the motor completely out to fix a bad wire. that trucks been running like a champ for 2yrs now.

As one Vet to another, thank you for your service brother...Honorably Discharged SSgt/E5, USAF

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2003 Pontiac Bonneville SSEI
3.8L V6 SC, 180*T (Drilled),
Custom PCM w/Perf Shift,
SLP Ceramic Coated Headers,
Thrasher Cold Air Intake,
GXP Tails, Interior Door handles, Trim pieces etc.
40th Aniv Grand Prix GTP Wheels (Very Shiny & Very Annoying )