Going in Limp home mode home but no apparent codes related to it...

[joegr]

Hey 2005 LS V8
(2nd mechanic said he found these codes:
U1027 - Engine RPM - Parking Brake
U1262 - BUS - PCM Relay

Says coils look pristine and he's confident they aren't the issue. He swapped the horn relay that is rarely used with the PCM relay, which is constantly used. No limp so far. Horn still works.)

Did swapping the relays resolve the U1262 code?

U1262 SCP (J1850) Communication Bus Fault
This DTC can come from any of these:

• SCP communications network circuits open, short to ground, or short to voltage
• DLC C251
• interior AJB C283a
• interior AJB C283b
• interior AJB C283c
• interior AJB C283d
• joint connector No. 4 C223
• joint connector No. 5 C427
• in-line C315
• ABS/TC module
• PCM
• DATC module
• ACM
• FEM
• REM
• DSM
• DDM
• instrument cluster
• navigation system module
• electronic parking brake module

The PCM relay or being loose in it's socket can be the cause, but there's a lot of other stuff it could be. The code certainly does not say "PCM relay." They may have included that as it may be a common cause.

The fact that the U1027 came only from the parking brake, and not also from the ABS and the FEM, makes it seem less likely to be the PCM relay, but I guess time will tell.

 

[2005_LS_V8]

So, I finally got the Coil code and had the coils and plugs replaced. There was a leak in one of the manifolds that was making it appear there was an oil leak on the back of the engine. That's fixed. Mechanic said plugs were fouled. EGR valve was bad, replacing that fixed my rough idle. They were charging $88 each for the Motorcraft coils, they gave me a discount back to market at $50. Still, it cost about $1,500 including synthetic oil change.

ECM failsafe code STILL comes on, once since I had this work done. Gas mileage improvement: zero! Drives like a bat out of hell again though, so that's nice. So smooth. I've had so many little things done to this car, and big things, I love it when it's running good. And no payments!