Diagnose and fix Jeep Liberty P2181 and U0401
Shops are reporting a high number of Jeep Liberty P2181 and U0401 conditions. In some cases you may also see a lightning bolt warning light indicating a throttle body problem. Other symptoms include the coolant temperature gauge moving to cold even though the engine is warm. Shops have scanned the engine using an infra-red thermometer and recorded actual temps of 194°F even though the gauge reads cold. However, if you shut down the engine and restart, the gauge reads normal and the U0401 code is gone. The issue happens when idling or driving at highway speed.
P2181-COOLING SYSTEM PERFORMANCE
U0401-IMPLAUSIBLE DATA RECEIVED FROM ECM/PCM
Chrysler service bulletin 18-015-11 Rev B
Chrysler has issued a service bulletin to address the P2181 and P0S0D trouble codes on 2007-2010 KA, and KK models with the 4.0 and 3.7L engines. The bulletin advises the shop to install new software to correct the problem.
Additional information on Jeep Liberty P2181 and U0401
The P2181 is what causes the U0401 code to set, so start by correcting the P2181 problem first.
If the software updated doesn’t fix the problem, shops are finding a faulty thermostat as the root cause in most cases. Shops insist on using an OEM thermostat as aftermarket thermostats don’t seem to fix the problem. Although, some shop have found a faulty engine coolant temperature sensor and even intermittent wiring to the engine coolant temperature sensor.
The only way to conclusively evaluate the engine coolant temperature sensor is to graph it using a scope. Shops are seeing glitches and incredibly fast “rate of change” in engine temperature that sets the code during the drive. Since you most likely don’t own a scope and since these are fairly inexpensive parts, it might pay to replace them if you can’t test them.
©, 2020 Rick Muscoplat