Service idle air control and error code P0550

[915caddy]

Hello all,

I have a 1999 Deville with 118k on the odometer. Recently the car was leaking coolant from the main crossover gaskets and after checking the forum for what needed to be done to fix it, I had a more mechanically inclined buddy help me (and by help me I mean do it for me). The leak is now fixed but I have a new problem. When I reach highway speeds (65mph) the dash displays "service idle air control." When I slow back down to a stop, my idle rpm is now at 800rpm instead of 650. I checked the codes and I get a PCM 0550. If I clear the code, the rpms go back down to normal idle. We are going to check all the hoses and electrical connections on Sunday to make sure everything was put back together correctly but this forum has been so useful in the past I figure one of you guys can point me in the right direction before I begin.

Thanks much,

Ben

[BodybyFisher]

Hello all,

I have a 1999 Deville with 118k on the odometer. Recently the car was leaking coolant from the main crossover gaskets and after checking the forum for what needed to be done to fix it, I had a more mechanically inclined buddy help me (and by help me I mean do it for me). The leak is now fixed but I have a new problem. When I reach highway speeds (65mph) the dash displays "service idle air control." When I slow back down to a stop, my idle rpm is now at 800rpm instead of 650. I checked the codes and I get a PCM 0550. If I clear the code, the rpms go back down to normal idle. We are going to check all the hoses and electrical connections on Sunday to make sure everything was put back together correctly but this forum has been so useful in the past I figure one of you guys can point me in the right direction before I begin.

Thanks much,

Ben

DTC P0550 Power Steering Pressure (PSP) Switch Circuit

Ah Ha, One of the faults is

PCM limits desired idle speed to a minimum of 800 RPM.

Check if the power steering pressure switch is open. The switch is down on the rack, maybe the connector got pulled during the crossover job, also check the engine compartment relay center, the CRUISE fuse feeds the power steering pressure switch

[915caddy]

Hello all,

I have a 1999 Deville with 118k on the odometer. Recently the car was leaking coolant from the main crossover gaskets and after checking the forum for what needed to be done to fix it, I had a more mechanically inclined buddy help me (and by help me I mean do it for me). The leak is now fixed but I have a new problem. When I reach highway speeds (65mph) the dash displays "service idle air control." When I slow back down to a stop, my idle rpm is now at 800rpm instead of 650. I checked the codes and I get a PCM 0550. If I clear the code, the rpms go back down to normal idle. We are going to check all the hoses and electrical connections on Sunday to make sure everything was put back together correctly but this forum has been so useful in the past I figure one of you guys can point me in the right direction before I begin.

Thanks much,

Ben

DTC P0550 Power Steering Pressure (PSP) Switch Circuit

Ah Ha, One of the faults is

PCM limits desired idle speed to a minimum of 800 RPM.

Check if the power steering pressure switch is open. The switch is down on the rack, maybe the connector got pulled during the crossover job, also check the engine compartment relay center, the CRUISE fuse feeds the power steering pressure switch

Fixing loose connection did the trick. Sorry for the delayed response. Thank you very much.