What next?
My '90 2+2 sometimes runs, but quits after it's driven a couple of miles (warmed up?).
My ECU code is 21 sometimes, then 55 sometimes. If I put the ECU in diag mode while running, it's 41.
I've cleaned & reseated the PTU connectors & have totally bypassed (carefully ohm'd each) the connectors to the harness.
I've cleaned & reseated each of the coil connectors and each of the injector connecors.
I've cleaned & reseated the CAS connector.

Anyone...?

 

What are code #'s 21 & 41? When it quits, does it stumble and die? does it have electrical power where it cranks over but doesn't fire? Or, does is shut off and there's nothing? What are the conditions when it dies?

 

When it quits, it just totally stops dead. It cranks, but no spark (I put a plug to ground with the #2 coil out & connected).
After a long time (perhaps cooling down??), it starts fine, then fails again after just a couple of miles of driving.
I believe that ECU code 21 is for a bad PTU connection (though I've cleaned & reseated both PTU connectors... perhaps I have a bad PTU). I believe (not sure) that ECU running code 41 means a problem with the air temperatur sensor ciruit (correct?).

 

http://www.ttzd.com/tech/diagnostictech.html

According to the diagnostics page above, code 21 is the ignition signal circuit. So, checking the ptu is the right idea.
However, there is no code 41 on the list. Doesn't mean it doesn't exist.
If it's an air temp circuit, i don't see how that would prevent the car from starting.

 

How can I check the PTU, other than getting a replacement?

What component would fail just because the car has waarmed up?

 

You know,...there is a recall on the PTU for the 1990's. Has yours already been replaced?

 

yea...ive got a sticker on my hood saying that it was replaced...let me know if you need to see what it looks like

 

https://www.zdriver.com/forum/showthread.php?t=6551

here's a pic of the new vs old ptu.