P21D1 Cylinder 3 Injector B Circuit/Open

[50TAJHY]

I’m hoping someone can help or at least chime in, because I’m a few parts away from throwing a match at this car. I have a 2019 Mustang GT PP1, FBO on E85 with a Holley High Ram.

One day on my way home from work, the car threw a cylinder 4 PI injector code. I bought a new set, installed them, and the car ran fine for an hour or two — then it threw a P21D1 code.

I pulled all 7 DI injectors, had them cleaned and flow-tested, and replaced the #8 injector with a new one. Put everything back in, and the same code came back. The car idles horribly, sounds like it’s down a cylinder, and makes a weird pinging noise. It sputters badly from 1500–3000 RPM.

Here’s what I’ve replaced so far, with no improvement:

• Spark plugs
• MAF sensor
• Low-pressure fuel pump
• High-pressure fuel pump
• Passenger-side DI injector harness

Much of this stuff was getting old anyway, so I didn’t mind replacing it, but none of it has fixed the issue. VCT solenoids are fairly new, I tested them, and they’re working correctly. I compression-tested all cylinders and got 180+ across the board. The manifold, throttle body, and intake all show no leaks — I triple-checked.

I sent my tuner a log, and he says it looks lean on Bank 1, but nothing I replace changes anything. I haven’t found a single forum post with this exact problem. At this point I’m starting to think it might be the PCM.

Sponsored

 

[Cloan]

A circuit/open code usually indicates a fault with the wiring instead of a mechanical fault. I don't have a wiring diagram on hand to point on the wires you'd need to check, but I'd start with ohming out the wiring for your injector. It's possible that you have a broken wire or corroded wire that is causing the code to set