Sounds like a plan. Nice! Go get 'em!!

 

Beautiful car. Looks like mine without the race additions.
Just curious- what does 8 mph addition mean to you?
More speed, of course, but how much in a straight, for example.
Sorry for the newb question. but curious.

 

Add- 8 hp instead of mph, of course.

 

Both the HP and TQ curves changed slightly, and that's where a small 8-HP might help. Corner exit speed directly impact straightline speeds and that's one of the things we'll try to figure out tomorrow. Honestly, I hope the HR just runs reliably and predictably. Then, it's time for the nut behind the wheel to find some extra time for a fast lap. Pueblo Motorsports Park is one of the best road racing circuits around, with a long front straight, slightly banked long radius first turn and elevation changes throughout. Top speed in the Z will be the 120-MPH range, but you must balance that with a 30-MPH hairpin with multiple shifts in between. It's a driver's track and this will be the first time we've run it in two years.

 

This season has been one of the most frustrating of my 33-year racing career. After loading up my Z33, we got down to Pueblo Motorsports Park (PMP) for testing only to have the Z exhibit some bizarre brake problems (LF locking intermittently on out lap) before having limp mode kick in down the front straightaway! Checked traffic before pulling to the inside and waiting to be towed in. We tried scanning for codes and found the same P0603 code as before. That one indicates "Internal control module keep alive memory module (KAM) error". WTF?

Erased that code and while it didn't return, I found P2138 (TB malfunction) kept coming back in the ECM section, as did the ABS code C1131. Both codes indicate a problem with the ECM properly functioning, but this is the second new 23719-EV12c ECM after the original EV12a unit failed. Is it possible my Z is EATING these components like sushi at the buffet table?

At this point, I haven't even got a good hypothesis to go on for repairing the T3 Z. Perhaps there's some interaction between ABS and ECM systems that's degrading the ability to open the TBs and triggering limp mode? It's a mystery that's destroying my SCCA race season. I'm already too far behind a Porsche driver to defend my 2020 T3 Divisional championship and the 2021 Mid-America Majors title is also beyond reach. Still hoping to qualify for the Indy Runoffs, but that's slowly slipping away if I can't get this figured out pronto!

 

Ouch, that's f'd up. Wish there was something I could do, David, cuz this just aggravates me even if they're not my problem!

OK, here's devil's-why-not question.... Why do you surmise the problem is a malfunctioning ECM *VERSUS* a fault at the reported site of malfunction, e.g. TB, ABS, etc.?

The more I think about it though, another question... Are you having CAN communication errors (U1000). Is it possible that the ECM isn't properly grounded? That is, something gone fritz in the harness? I recall a friend who's Z did some weirdo stuff in the ECM and I mentioned to him, "sounds like something's not grounded". Turned out to be a harness ground... that wasn't adequately grounded.

Just a couple of thoughts. I'll sleep on it and see if anything fresh pops into my tired brain in the morning.

 

I was just going to say, if the car is eating ECM's, it's probably a bad ground at the ECM. Check them.

 

Taking Mic's suggestions to the next step, I've disassembled the electrical section near the battery and IPDM. Checked the grounds for all, including the ECM and disassembled, sanded and reassembled all grounds. Yet I still show a U1001 for CAN communication error, but this code has shown up consistently since this Z33 was converted for racing. Worked just fine for 12 years and suddenly BOOM! No throttle, no TB control and NO FUN.

Next step is to start on the diagnostic chart for the ABS code C1131 that continues to identify ECM malfunctions. Here's the text from the FSM:

On Board Diagnosis Logic NBS000GZ
These self-diagnoses have the one trip detection logic.
PBIB1741E
MONITOR ITEM CONDITION SPECIFICATION
ACCEL SEN 1 ● Ignition switch: ON
(Engine stopped)
Accelerator pedal: Fully released 0.5 - 1.0V
Accelerator pedal: Fully depressed 4.0 - 4.8V
ACCEL SEN 2*1 ● Ignition switch: ON
(Engine stopped)
Accelerator pedal: Fully released 0.3 - 1.2V
Accelerator pedal: Fully depressed 3.9 - 4.8V
CLSD THL POS ● Ignition switch: ON
(Engine stopped)
Accelerator pedal: Fully released ON
Accelerator pedal: Slightly depressed OFF
DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P2127
2127
Accelerator pedal posi tion sensor 2 circuit low
input
An excessively low voltage from the APP sen sor 2 is sent to ECM.
● Harness or connectors
(APP sensor 2 dircuit is open or
shorted.)
[CKP sensor (POS) circuit is open or
shorted.]
[CMP sensor (PHASE) (bank 2) circuit is
shorted.]
[EVT control position sensor (bank 2) circuit is shorted.]
(EVAP control system pressure sensor
circuit is shorted.)
(Refrigerant pressure sensor circuit is
shorted.)
● Accelerator pedal position sensor
● Crankshaft position sensor (POS)
● Camshaft position sensor (PHASE)
(bank 2)
● Exhaust valve timing control position
sensor (bank 2)
● EVAP control system pressure senso

 

And here I was complaining about having to replace a throttle CABLE to the carburetors (what's that?) on my roadster. Yeah, not too reliable at times but at least a throttle cable is an SPF versus the thousand of possibilities and required values on our "modern" Zs.

 

I just did a bunch of reading on this and found the following... The ABS code comes on because it's one of the two termination modules of the CAN system. When there's any problem on the CAN system, this code can pop up. I also found that many times there's a problem with the throttle body when this code pops up. Because you had a TB code, I believe you're problem is TB related. Some people fixed the issue with a new TB. For some the issue was a wiring issue. The third fix was sometime the sensor on the throttle pedal. It's going to be on you to figure which. I'd start by checking continuity on all of the TB wires. Make sure you wiggle the wires while checking them.

 

I'll have to check continuity with both TBs as I run the HR. Already replaced the throttle pedal sensor 3X. And since we've already gone through the entire engine harness, the next step might be replacing the IPDM.

 

Some progress to report- replacing the IPDM seems to allow startup, steady idle and throttle control of the racecar. Fingers crossed, but we'll have to test to see how stable this solution will be. New LF wheel speed sensor revealed some problems with the connector on the inside of the wheel well. Let's see how a new one will affect the ABS codes when everything gets put together for further testing.

 

The mystery deepens: while the IPDM replacement is functioning perfectly, limp mode comes back as soon as the car moves even an inch. No codes return to the ECM, but the ABS section shows C1131 (ABS reading ECM problems) continuing to appear. This does not happen unless the HR is started and running with tranny engaged. The TBs check out and run fine right up to the point that C1131 stops the show. After that, it merely idles and make this a fine showcar.

The new LF wheel speed sensor is functioning perfectly, and there's clearly plenty of signal getting back to the ABS section, so that another new part that didn't really solve any problem. It occurs to me that I often criticize others for "throwing parts at the car" when they first experience a problem, rather than use the onboard diagnostic system. But this problem seems to defy that logic, as the diagnostics seem at odds with one another. It's blowing my mind, but I still want to understand the problem(s) going forward.

 

Weekend report: checked the TB continuity on both banks and they were OK. Went back over both the interior fuses (10 amp engine control and electronics fuses) and confirmed they are both intact and functioning. Did some gymnastics to take a closer look at the ABS control unit under the steering column, but uncertain if that's just another part that I'd be replacing needlessly. Time is growing short, even though the next SCCA Majors race is next weekend. Five Porsches and me are entered in T3- normally, I'd be excited at the prospect.

 

Rooting for you dk. Hope you can get it figured out.

 

While this thread hasn't been updated for several weeks, it's not because of a lack of effort. The problem is the multiple tests, part changes and checks have still not turned up the culprit(s) and the T3 Z remains stubbornly grounded. TB continuity checks out, and the ABS pump unit replaced, bled and checked. No joy. The dyno shop where I had the car tuned with the restrictors thought they could eliminate the C1131 code with their updated UpRev software, but discovered it was so deeply buried in the OEM code that it could not be done. They gave the Z back with the comment that the diagnostic pathway I'd followed was valid and the work properly done. Small consolation, but hey, at this point, I'll take any positives I can get.

Currently, I just got finished inspecting the taillight connections and making sure the wiring to the back is intact, with no possible grounding issues. Next, there's a three plug relay near the ABS pump unit that I'll try replacing on the off-chance it's defective and sending a bad signal to the control unit. This is just a guess, but at this point, that's what I'm down to. Most of the SCCA season is done and I won't qualify for the Indy Runoffs this year. Bitter pill to take, but I'm not giving up...

 

Uggggh.

Not sure what else to say besides that.

Every time I curse my carburetors and other old school, non-e-controlled devices, I’m reminded of the old adage “To err is human but it takes a computer to really screw things up.”

Again, wish there was something I could do!!

Oh wait, there is! Not car related but will help! Back at you later!

In the meantime, hang in there!!