Experiencing issues with your 2011 Jeep Liberty and its OBD2 plug-in? Many Jeep Liberty owners and auto repair professionals encounter situations where diagnosing problems becomes challenging due to a lack of communication through the OBD2 port. This article delves into a specific no-start, no-crank scenario in a 2011 Jeep Liberty, highlighting potential issues related to the OBD2 system and CAN network communication.
One recent case involved a 2011 Jeep Liberty brought in for a no-start, no-crank condition. Interestingly, upon arrival, the vehicle unexpectedly started when rolled off the flatbed tow truck. It ran without any warning lights and seemed perfectly normal for a couple of days. However, the problem resurfaced. The remote key fob failed to unlock the doors, and manually unlocking with the key triggered the factory alarm. Turning the ignition key resulted in no response – no dash lights, no engine crank. Disconnecting and reconnecting the battery silenced the alarm but did not resolve the no-start issue.
Upon initial inspection, some electrical systems were still functioning: the instrument cluster lit up, the radio and HVAC system worked, and the rear windows operated, but the front windows did not. Connecting a scan tool revealed a significant communication problem. While the tool auto-identified the vehicle, it could only establish communication with the Totally Integrated Power Module (TIPM) on the CAN “C” network, and the TIPM itself showed no fault codes. Communication with modules on the “IHS” CAN network was normal. A CAN bus resistance check between pins 6 and 14 of the OBD2 port showed a correct 60 ohms. However, when observing the CAN network with a scope, both CAN high and CAN low lines were flatlined at 2.5 volts as soon as the ignition was turned on. Adding to the confusion, the PRNDL indicator lights in the instrument cluster were flashing erratically, and the red temperature warning light was flickering.
To isolate the communication fault, a systematic disconnection of modules on the CAN network was performed, excluding the SRS module due to time constraints in accessing it. Despite disconnecting various modules, the communication issue persisted, with the CAN lines remaining flatlined at 2.5 volts at every module checked. Power and ground supplies to the Powertrain Control Module (PCM) were verified to be in good order, and the 5-volt reference voltage was present and functioning. All ground connections under the TIPM and near the brake master cylinder, which appeared corroded, were cleaned and re-secured. The ignition switch was confirmed to be working correctly using a test light and by observing TIPM data. Notably, the instrument cluster had a stored diagnostic trouble code related to communication with the TIPM, although it was not a current fault.
This situation points towards a potential issue within the CAN C network that is causing a communication breakdown, preventing the OBD2 plug-in from functioning correctly for most modules and resulting in the no-start condition. Further diagnostic steps should focus on thoroughly investigating the CAN C network wiring for shorts or breaks, and deeper testing of the TIPM itself, as it is the only module communicating on that network. Isolating sections of the CAN C network to pinpoint the short or faulty module will be crucial in resolving this 2011 Jeep Liberty’s electrical and communication problems.
