OK guys, looking for some insight here.... I've spent too much time chasing down ghosts in this truck, and I'm guessing there's something I'm missing.

D21 with 178k miles, throwing the following codes:

P0335 (CPS Sensor / Circuit; ESS Sensor / Circuit)
P0705 (PNP Switch / Circuit; Shift position sensor circuit; Trans range sensor)
P1130 (Swirl control solenoid / valve).

Any possibility that ONE thing is kicking off all of these codes? She runs good, maybe a little low on power, but no overheating or weird noises.

Do they share a ground wire? Given the harness layout on the D21's, that seems plausible.

Good question - I will dig through and see.

VStar650CL wrote: ↑

Mon Aug 23, 2021 7:46 pm

Do they share a ground wire? Given the harness layout on the D21's, that seems plausible.

So, my strengths admittedly do not lie in translating spaghetti... I'm looking at the harness layout and for the life of me can't determine any commonality between the components that [theoretically] are causing these codes (crank pos sensor, PNP / inhibitor switch, swirl control solenoid).

It's a MT, so I'm not even sure how the inhibitor switch comes in to play (unless it's secondary to the other issues).

I went through all three, and unless there are trashed wires together somewhere, I don't see any relationship. I can tell you how to diagnose all three separately, maybe that will lead you somewhere.

P0705: On an M/T the ECM throws this when it sees the switch showing N even though the truck is moving. There should be a reference voltage on the Blue/Black wire with the connector unplugged. If there's nothing then you have a bad wire or connector between the Neutral Switch and ECM. The Black wire should be a good ground, and with the connector back-probed, you should see 0V in N and the reference voltage in any gear.

P0335: The crank sensor is actually a 2-wire inductive, the 3rd wire (Black) is actually a shield ground. Black/Green is a bias ground supplied through the ECM and should show near 0V in operation. Red is the signal wire and should show above 200mV AC at idle with an increasing voltage as RPM's rise. The D21 ECM only uses the CMP for misfire detection, so a malfunction won't cause symptoms like on later models.

P1130: The ECM throws this code when it sees an open or shorted coil in the swirl solenoid or the vacuum check switch shows the vacuum not changing in response to the solenoid. Here's how the system works: The swirl solenoid is grounded by the ECM at idle and low RPM, sending vacuum to the control valve to close the butterflies. The ECM should kill the ground above 3600 RPM, removing vacuum from the control valve and opening the butterflies. The vacuum check switch tells the ECM if there is vacuum to the valve. The Red/Yellow wire at the switch is pulled up to 5V by the ECM and grounded by the switch when it closes at high RPM, so the signal voltage should go from 5V to 0V when the runners operate. If it stays at 5V then the ground wire may be bad. I can't find a resistance spec for the control valve coil but it can't be too low, probably 10~20 ohms or so. You should be able to power it externally and see if it opens and closes the valve. If it does, then chances are the switch has a problem and not the valve.