Code 37 idle speed control fault

[olypopper]

I've got a buddies sled that has a code 37. I searched alot of posts and didn't find much on the topic of code 37 so figured I'd post some pictures and what happened in hopes to help out someone else in the future that may have this problem show up.

In a nutshell, this code means the ecu has lost the ability to control engine rpm via the idle speed controller that is mounted on the throttle body assembly. There are several troubleshooting steps listed under diagnostic code 54 but to the laymen, they don't mean much. What a guy needs to know is how this idle speed controller is controlled by the ecu. The sled provides power directly to the valve through a pair of red/yellow wires at key on (center two connections at ISC valve). The valve is then controlled via the outer 4 wires (there are 6 total wires going to the valve).

I started my testing by attempting to run the diagnostic test via the gauge cluster but the valve gave no response when commanded (it should make a quick rattling noise). At that point I stripped the sled down to gain access to the throttle body and ISC valve. The valve tested good via the resistance check (57-63 ohms at room temp). I then tested the 4 signal wires from the ecu to the ISC valve for resistance and continuity. I also used a small light bulb to test for high resistance on each wire and they all passed. This is when I tested for power to the valve at key on. The red/yellow wire that feeds power to the IS valve had no power present. I had previously inspected all the fuses and grounds and knew they were good. I worked my way backwards to the fuel injection harness connection on the left side of the sled (big white/grey connector above and inboard of the clutches) and found no power on either side of that connector. At that point I inspected the harness carefully and found a serious rub mark/cut in the center of that harness directly beneath the upper steering post mount. I had already removed the steering post to gain access to everything else. Once I cut through the harness sheath it was clearly obvious what the problem was. The main power feed was cut/corroded in two. I tested the red/yellow wire at the key switch and had power. I also tested the same color wire at the ECU and had power. Once I repaired the damaged section of harness and plugged everything back in, the code was still present until the engine had been run through a start up/shut down cycle. The code cleared once the engine had run without the symptoms present. This seems like a bad spot on a Nytro and I'm sure it's not the only one to have this problem. The sled has 6k miles on it, almost no trailer time as it lives on the Yukon river many miles from any road.

I hope this helps someone in the future to keep their Nytro running and avoid a dealer throwing parts at it.

 

[MrSled]

I've got a buddies sled that has a code 37. I searched alot of posts and didn't find much on the topic of code 37 so figured I'd post some pictures and what happened in hopes to help out someone else in the future that may have this problem show up.

In a nutshell, this code means the ecu has lost the ability to control engine rpm via the idle speed controller that is mounted on the throttle body assembly. There are several troubleshooting steps listed under diagnostic code 54 but to the laymen, they don't mean much. What a guy needs to know is how this idle speed controller is controlled by the ecu. The sled provides power directly to the valve through a pair of red/yellow wires at key on (center two connections at ISC valve). The valve is then controlled via the outer 4 wires (there are 6 total wires going to the valve).

I started my testing by attempting to run the diagnostic test via the gauge cluster but the valve gave no response when commanded (it should make a quick rattling noise). At that point I stripped the sled down to gain access to the throttle body and ISC valve. The valve tested good via the resistance check (57-63 ohms at room temp). I then tested the 4 signal wires from the ecu to the ISC valve for resistance and continuity. I also used a small light bulb to test for high resistance on each wire and they all passed. This is when I tested for power to the valve at key on. The red/yellow wire that feeds power to the IS valve had no power present. I had previously inspected all the fuses and grounds and knew they were good. I worked my way backwards to the fuel injection harness connection on the left side of the sled (big white/grey connector above and inboard of the clutches) and found no power on either side of that connector. At that point I inspected the harness carefully and found a serious rub mark/cut in the center of that harness directly beneath the upper steering post mount. I had already removed the steering post to gain access to everything else. Once I cut through the harness sheath it was clearly obvious what the problem was. The main power feed was cut/corroded in two. I tested the red/yellow wire at the key switch and had power. I also tested the same color wire at the ECU and had power. Once I repaired the damaged section of harness and plugged everything back in, the code was still present until the engine had been run through a start up/shut down cycle. The code cleared once the engine had run without the symptoms present. This seems like a bad spot on a Nytro and I'm sure it's not the only one to have this problem. The sled has 6k miles on it, almost no trailer time as it lives on the Yukon river many miles from any road.

I hope this helps someone in the future to keep their Nytro running and avoid a dealer throwing parts at it.

Great find!! I had this happen to my Nytro, years back but instead of throwing a code 37, it would blow headlight fuse.