Eegads, the misinformation here is BRUTAL!
Okay, to start, here's how Diagnostic codes work. And frankly I cannot BELIEVE the Ford tech didn't know this. He should be fired.
Codes do start with a letter. Like P0xxx, P1xxx, P2xxx, P3xxx. Those are all POWERTRAIN codes, 400 of them (hence the P). They refer to powertrain (engine, tranny) functions as well as emissions systems. Then you have C0xxx-C3xxx These are CHASSIS codes. Then you have BODY codes, B0xxx-B3xxx, and COMMUNICATION codes, U0xxx-U3xxx. That's 1600 codes.
Now, in a computer, you need to represent these codes as 16-bit numbers. There is no P or U in a computer, we use hexadecimal, so with a bit of manululation you get:
P0xxx = 0xxx
P1xxx = 1xxx
P2xxx = 2xxx
P3xxx = 3xxx
C0xxx = 4xxx
...
C3xxx = 7xxx
B0xxx = 8xxx
... (remember hex digits, 0-9,A,B,C,D,E,F)
B3xxx = Bxxx
U0xxx = Cxxx
...
U3xxx = Fxxx
Soooo, in short, 5284 = C1284. Your Ford tech should have known that. GM uses the exact same code structure, I know that for a fact, and I'd bet Chrysler does too.
As to the code itself, it's not an emissions code**, it's an Oil Pressure Switch code, just like the description says. And it's not an uncommon one - SEVERAL 99+s show this code ON THE CLUSTER occasionally, it's nothing to worry about. There's probably a slight blip in the oil pressure signal from the sensor, and the cluster picks up on it and sets the DTC.
It's correct that the cluster codes have nothing to do with codes that may or may not be in the EEC (they're the same codes numerically and mean the same, but a code set in the cluster does not mean the code is set in the EEC as well, and visa versa). The cluster sees the oil pressure signal from the sensor just the same as the EEC does. The fact that the CLUSTER has set that code while the EEC hasn't (if the EEC had set it too, you'd have a SES) just means that the cluster is more picky (probably TOO picky) about that particular diagnostic routine than the EEC is.
Ford, I'm sure, knows about this issue, but since it's a diagnostic issue, and not a problem with the switch itself, and since only the CLUSTER usually detects it, and no SES is usually set, there's really no reason to do anything about it.
Particularly when Ford's own mechanics don't seem to know how to read codes properly.
Edit: Just saw that you ARE getting a SES. If your gauge is still reading okay pressure, and the car runs fine, then it's more than likely it's the same 'blip', just bad enough that the EEC is setting the code in addition to the cluster. I'd bet if you cleared it, it'd go away. If it keeps coming back, I might check the oil pressure sensor connector and terminals, or maybe replace the sensor. Either way, your engine is OKAY. It's just that top-notch Ford quality coming through.
**Note DTCs certainly CAN have to do with emissions. Several of the Powertrain codes are devoted to emissions systems such as EGR, catalyst operation, and fuel tank/canister systems. If the EEC detects an issue that would seriously affect emissions (like an EGR problem), it will set the appropriate code just as if it were a performance issue. Caveat being that usually emissions diagnostics are much 'softer', i.e. they are more loosely calibrated and generally take longer periods to set.
