Code 53 - Spirit R/T with 'Stg 4' SBEC

[iTurbo]

Got a problem with a Spirit R/T that a local friend now owns. It was recently upgraded with a bunch of go-fast stuff including:

T04E 50-trim turbo
FMIC
FWDP Stg 4 SBEC
+40 injectors
3-bar MAP

After installing the FWDP SBEC, my friend said it had a random misfire and backfire. I drove the car today and sure enough, it had a random misfire where the power was cut (like total ignition cut) and the tach would drop to zero when this happens with a small backfire out the exhaust. I believe the backfire is due to the unburnt fuel in the exhaust as a byproduct of the ignition cut. The car runs pretty good (when it does run) and I don't believe there are any timing issues.

Tonight it got so bad that the car will barely start. If it does, the ignition is dropping out so much it stalls after a few seconds and the tachometer is freaking out. I checked the codes and got 25 (AIS motor) and 53, which my OTC scanner describes as a ECU self-test failure. Is the code 53 something I should expect with a recalibrated SBEC or is this sounding like a SBEC failure? I have poked around the wiring harness a little bit but so far can't find anything obviously wrong. All the fuse links seem good as well.

Any ideas?

[ShelGame]

Even in the TIII, the Code 53 only represents a checksum failure. Most likely, this is due to the custom cal.

However, (speculation here) it could also be a chip with some bad memory cells (which is really the only thing the checksum could find outside of a custom cal). The bad memory cell would most likely cause a COP reset, which might give you a misfire as the ECU 're-boots'. It's also possible that the ECU would just shutdown. I've never actually had that happen. Usually, if the chip goes bad, the whole thing just won't read or write anymore. In which case, you'd have a no-start.

[iTurbo]

Thanks Rob. I have a feeling this might be wiring related. My friend came over last night and it sure seemed like it got a lot worse after poking around the wiring harness under hood. I have a hunch it's possibly an intermittent short or open in the Z1 feed or an intermittent connection within the 60-way SBEC connector.

[iTurbo]

I started the car up after work today and it fired right up and idled perfectly as if nothing was ever wrong! I was all set to swap out the SBEC with a stock unit just to see if that cleared it up, but I didn't bother.

While it was warming up, I tugged on various parts of the underhood wiring harness to see if I could recreate the problem, but nothing seemed to affect it at all. One thing I remember doing last night was that I had erased the fault codes with the OTC 4000E with the car running. We took the car for a short trip around the block right after that, and that's when it got waaaay worse, so maybe the aftermarket cal freaked out about the codes being reset with the car running and not shutting down/restarting. I have no idea, but the problem seems to have disappeared for now.

[2.216VTurbo]

My TIII Rampage has a code 53, I thought it was a 'nonsense code' or is that what you were explaining Rob?? We've been drinking by the pool all day at the Marriot in Palm Springs so I may not be comprehending... The 53 is the reason I failed CA emissions testing a few years ago, the BAR referee wouldn't pass it with codes stored

[ShelGame]

Its mostly a nonsense code. If it really indicated a problem, the ECU wouldn't work.

FWIW, I can fix the 53 easily using MP Tune...

[iTurbo]

I'm pretty sure I found the reason for the engine cutting out. There was an intermittent connection inside the 60-way SBEC connector. It tuned out the pin #18 (ignition coil driver #2) was worn to the point it was loosing contact with the pin. I could make the car stall at will when I wiggled the wire.I removed the red plastic insert and gave it a nudge with a jewelers screwdriver to make the inside diameter of the pin slightly smaller and it seems to be working so far.

[86Shelby]

I checked tonight and my FWDP cal does not have the code 53.

[supercrackerbox]

My Charger has a code 53, and the Daytona used to have it while I had the MP SBEC in it.

[Force Fed Mopar]

Resurrecting this because I just got a 91 RT build started today using an FWD-P Stage 4 SBEC straight from them (not second-hand)and it is stupid rich and won't idle unless I uncork a 3/8 vacuum port. Has codes 35 and 53.

[DoubleD]

What is the fuel pressure set at?

[Force Fed Mopar]

Set to factory setting. It had some old fuel in it, and also has multiple fuel leaks. Found out that code 53 is normal with their modified SBEC's. It is idling now. Seems to be a little better every time I run it.