MIL Request Circuit
Diagnostic Trouble Code
(DTC) P1700 indicates that a transmission related On-Board Diagnostics II
(OBD II) failure has occurred. The Transmission Control Module
(TCM) controls a dedicated Service Transmission Lamp
(STL) which illuminates when a fail is reported by certain non-emissions related TCM diagnostics. The TCM has no direct control of the engine
Malfunction Indicator Lamp (MIL), but if a transmission fault occurs that is emissions related, the engine MIL must illuminate. A MIL Request circuit between the ECM and the TCM provides a means for illuminating the MIL, even though the fault was detected by the TCM. This circuit is pulled up to B+ within the ECM. In order to illuminate the MIL, the TCM pulls the circuit low. The ECM detects this low circuit and the DTC P1700 sets, which illuminates the MIL. If the ECM detects a problem with the MIL Request circuit, the DTC P1701 - MIL Request circuit will set.