Changed alternator on 2010 LR2. Pulled intake manifold so had to disconnected all of sendors attached to it to get it out. Installed new alternator and put it back together. Now when start it idles really rough, sputters and dies out. Threw a p0506 idle less than expected, p0069 switch long term failure, p0107 manifold absolute pressure sensor low input, and p2138 demand sensor pedal comparison. Implausible signal condition. Anyone experience these issues when doing this job and any suggestions. Thank you in advance.

 

Is your engine ground wire connected?

 

Initially battery light would come on periodically. When vehicle turned off battery voltage at 12.2, when started would drop to 11.6. Installed new alternator. When shut off voltage at battery 12.3, when rough idle 14.0 to 14.1.

When installed alternator put sensor wire and cable back on. 4 bolts through altnator into block.

When disconnect MAF sensor will rough idle for about 20 - 30 seconds before does out. When mad sensor connected does out in 1 - 10 sec typically.

 

Charge your battery up so that it is around 12.6 or more. Then try again. I would clear codes before the start with the new battery and then check for returned codes after trial start. As questioned before make sure your engine to body ground is attached and in good condition at connection points.

 

+1 to OldKarz line of questioning. Likely an electrical connection issue going on. I would also check the pins in all of the connectors you touched to make sure none of the pins got bent over upon reconnection. That said, are you sure all of the intake manifold oval gaskets stayed in place for reassembly? It's super easy to get one of them either pulled askew or damaged wiggling that manifold back into position. Not a lot of room to work there.

 

Thanks and will give all of these a try.

 

Did you use new intake gaskets? Those DTCs seem more electrical but super-lean idle due to vacuum leak might exceed sensor performance ranges.

 

Ground cable going from battery to body still tightly connected on both ends. Had disconnected from battery, not from vehicle. Tore apart again all pins look good and gaskets appeared to be in place. Reassembled. Charged battery up to 12.7 V. Still short rough idle then dies out. Ordering new gaskets, and map sensor. Throwing 3 different barometric pressure map errors. Also still throwing pedal sensor comparison error. More to follow when parts arrive.

 

The P2138 code indicates a mismatch from the pedal position to the throttle body position. I would check the throttle body connection

 

It is the ground from body to engine that needs checking. Not body to battery.