I've been getting these codes lately. I've cleared them and they keep coming back. I was hoping it was just an anomaly after resetting all computers when I grounded out the positive terminal by the battery. But it appears this is a real problem. My idle is fairly smooth and always around 700-800RPM. There is a slight vibration when idling. I was considering sending off the fuel injectors for a rebuild though it isn't bad. Anyways I'm not sure where to start here. Maybe the TPS? Any ideas or tips would be greatly appreciated.

 

For everyone's information: P0506 and P0507 are the codes for the A-bank idle speed monitor test faults (low and high).

Our friend Tcasmarcus recently got P1507 for the B-bank idle speed monitor fault, along with a MAP fault. Thread "High Fuel Consumption".

As I advised him, I would:
Check the integrity of the air tube between the MAP sensor and manifold. Blow through to make sure the little cylindrical filter is not blocked. If it is, then the idle check result might be out of range, and the code set. Also check the integrity of the main inlet and outlet hoses that connect to the Idle Speed Control Valves (The large tubes).

Check the throttle linkage to be sure it is secure and operating in absolute unison with the left side. Both throttles must start to open at the same time or the MAP readings will not match and it will throw the code. A common cause of mismatch is a worn out or missing throttle shaft bushing.

Removing and reseating the ISCV connector will insure good contact while the ECU tries to cycle the valve to run the check.

The ISCVs are on the left of this picture. I was replacing those worn out water tube bushings at the time.



Here's the left side all cleaned up and back home. Pretty, right?

 

Sleek Jag thanks so much for the info! I'll be checking all this today.

 

Sleek jag, thanks so much for helping me zero in on the problem. After checking all else and finding nothing wrong (brand new throttle bushings and id already checked/replace those hoses) I decided to pop off the the idle control valves. Just one hose and 4 7mm bolts real easy to take off. I found both of them real dirty. The A bank was so bad it wouldn’t turn which was the source of the codes I believe. So I cleaned them up, and checked resistance to compare both. Both measured a little over 40 ohms pin to pin, and exactly half of that from side to center pin. So I put them back on, also cleaned both throttle bodies which were also quite dirty, and noticed a big difference immediately when I started the car this morning. It idled at 1100 RPM for a while, then settled to 650 once warm and was so smooth I could barley tell the engine was running from inside the car. Cleared the codes and took it for a few test drives. It’s amazing how smooth these engines idle! I’m glad I didn’t waste money sending off the injector.

Thanks again for leading me down the right path!




Before

After

 

At the time of my repair, I was thinking only of the coolant pipes and gaskets etc. I didn't have an idle problem. I didn't even take apart the idle air valves to clean them. Hence that thought did not occur to me now. So thanks for returning the favor! Since they are easy to access and remove without disturbing the coolant routes (aside from the small bleed tube) I may go ahead and clean mine too. Makes sense that the A bank was giving both high and low fault if the valve wouldn't move.

Very happy to hear she's idling much better now. Well done!