No Crank No Start Ignition Run Circuit
This vehicle had an intermittent no crank/no start condition. No codes were stored in the PCM. There was a U1197-00 code in the Radio Frequency Hub (RFH). This module handles the anti-theft key fob functions. The code indicates that the Secur2 Seed Response from the PCM was not received. The DTC flow chart calls for reprogramming the PCM if there are no stored PCM codes. diag.net/file/fpo4bsrt9… Here is a power distribution diagram. This problem can actually be caused by s defective run/start relay, or a problem with the run/start bus bar. Both of these are located in the underhood fuse box near the battery. The relay can be replaced without replacing the fuse diag.net/file/fpo4bsrt9… diag.net/file/f5i98mnrc… The testlight in the photograph is pointing to fuse 157 that feeds power to the PCM with the start button in the run mode. Check for 12v at this fuse during the no start. If there is no power here, the PCM will not have ignition run power and cannot send the seed request that the RFH hub is looking for. Taping on the relay may restore operation. This will probably not resolve an issue with bus bar in the fuse box. The relay coil is energized by a high side driver in the BCM when the ignition is in "run".. This problem did not set any DTCs in the PCM . It did not cause a loss of PCM communication. If you try to program the PCM while this failure is present, you will receive a message from the programming device that states: " according to the PCM the ignition is not in the run mode". Also check for codes in other modules. Both the ABS and air bag modules set codes indicating that there was a fault with the ignition run circuit. Hope this helps. Thanks for reading.
Oh wow, good stuff. I only just found the "resources" section just today. (been a member for a year). You might not remember at this point, but could you monitor the ignition switch status on the scan tool to point you in the right direction to begin with. (in hindsight)