Besides my cruise control not working the day after getting the Check Engine Light flash code 31 I do not have low or high jake. I do have medium jake. I am also able to run high idle through the cruise control buttons. I'm using Detroit Diesel DDEC Troubleshooting Manual Section 31 Flash Code 31 - Engine Brake Fault Code. The SID / SAE code is 051. I do not know if it is FMI 3 or 4. According to the troubleshooting manual "Flash Code 31 indicates the engine brake low or medium circuit has an open or is shorted to battery ground." My question pertains to section 31.3.4 Check for Open that reads: 1. Turn vehicle engine OFF. 2. Disconnect 2-pin connector pigtail from engine. 3. Disconnect 30-pin engine harness connector. 4. Install a jumper wire between pins #561 and #562, ECM side. 5. Measure resistance between S3 (#561) and T3 (#562) of the engine harness connector. 5(a). If measured resistance is less than 5 ohms, refer to section 31.3.5. 5(b). If measured resistance is greater than 5 ohms, one or both wires are open. So - item 4 says to connect a jumper on the ECM from pin 561 to 562. Item 5 says to measure resistance on the engine harness connector. If the engine harness is disconnected from the ECM where are the connections made to measure resistance when the ECM is isolated from the engine harness connector and why jump the ECM pins? I must be missing something. Thanks.
It's probably a bad wiring harness for the jake, pull the valve cover and find the loose or broken wire,
Pulled off the cover. Sent power from the Engine Harness Connector, S3 and T3, and all 3 solenoids activate. Looks like I will need to check my input side at the Vehicle Harness.
