I am getting both codes. I have cleaned the throttle body with tb cleaner. The MAF is only about 3 months old, thanks to a dealer (didn't fix the issue). I have pulled apart very component from the air box to the intake plenum to verify that there are no leaks. The idle control valve is very clean and moving freely. I tested it with a 9 volt battery and it moved both open and closed. I tested it as well with an ohm meter and it pegged to 0 in all configurations and tested another unit in place, (not the ICV). I have not found any cracked or torn lines that I have noticed.

The vehicle runs fine, no noticeable issue other then upon periodic cold start-up. The engine will rev up and down for about 20 seconds then settles down to a normal idle. I have cleared the codes before attempting my efforts, but the both come back with-in a few cycles if not the first.

Thanks guys.

Phil

 

P0101 - ECU does not like MAF readings vs those computed from rpm and throttle position. Sensors involved include MAF, ECT, and TPS. Must be within an adaptive value, so not a hard number that does not change.

P0505 - ECU does not like RPM, it is 180 rpm too far one way, or 10 rpm too far the other.

You could have a worn TPS sensor (it is basically a volume control from an old syle radio, the pot or potentiometer can get noisy or develop a bad spot). You could have an out of spec ECT sensor.

 

I have swapped out both the tps and the ICV with take-off units with no change. The codes come back after a couple of restarts.

Question: should the ICV (idle control valve) hum from electrical current when you turn the key to the accessories position? It just seems a little loud. They both do it.

Can you give more background on the ECT? Thanks very much for your help.

Phil

 

The IACV is also called a stepper motor, it does move in/out as part of the process.

Here's more on the ECT (coolant sensor) - only one on a D2, separate ones on a D1 for gauge and ECU.

Now we've been talking about sensors. Have you noticed any coolant loss? If you had an "inside the engine" coolant leak, that got into one of the cylinders, it could make for rough running when started, until burned away. Might be a very tiny leak... now.

 

Savannah I am still struggling. I had a mechanic do some further testing and he says that the ECM is showing 5 grams of pressure even when the engine is not runnung and when the Maf is unplugged. He thinks the ECM is bad. He said that the Coolant temp sensor is testing out correctly. Any thoughts?

 

my D1 shows MAF of 0.00 not running, and 0.02 - 0.03 at cold idle (45 F, which is cold here). So if you have a sensor reading that does not make sense (like air flow when there is none) that sensor is unusual. Any warranty on it from the dealer?

See attached pages, lists things that can cause MAF to be off normal.

 

Phil, I have exactly the same symptoms and codes with my 2004. It's driving me crazy. Like you, there are no noticeable vacuum leaks, replaced TPS, replaced MAF.

On occasional cold start I also get the revving up and down until the idle settles down.

Did you resolve your issue and if so, what was the fix ? ECM as your mechanic suspected ?
Thanks!

 

Put a live code scanner onto the OBDII and get the intake temp and the coolant temp that the sensors are reporting.

Make sure the braided ground strap from the drivers's side cylinder head to the fire wall is in place to assure good signal ground.

 

Quick update on this thread for folks who encounter this problem in the future.
I spoke with Phil, he was never able to solve his problem and ended up selling his Disco.

Regarding my truck. Last sunday i removed and cleaned the IACV, didn't solve. I admitted defeat and called in my local Indie Rover mechanic (Jahn at Rovin Rovers) . As we speak he's installing a known good IACV to eliminate that as a source of the problem. From there he's thinking about turning his attention to the ECM. He's checked for vacuum leaks, bad grounds already. I'll keep updating until there's a solution to the problem

 

I should have just taken the truck to Jahn at Rovin Rovers straight away! I just heard from him that he found the problem. It was the reduction valve/metered air baffle on the valve cover PCV port.