1 Answer

Code 12 is set when the battery has been disconnected and the computer (ECU) has been reset. The power limited light will not light and limp mode does not apply. This code shows up when power to the computer has been interrupted as when the computer has been reset by disconnecting the battery.

Battery or power to the EUC disconnected – Code 12 is normal and doesn’t necessarily indicate a fault. If the battery has been disconnected or the electrical system has been worked on recently code 12 will indicate this. This code will is removed after about 15 engine starts.

Corroded Battery Terminals, Low Battery Voltage – Code 12 will be thrown if the system voltage drops too far below normal. This may be the result of a bad battery or the connection between the battery and the computer.  If the engine was jumped started and the battery terminals are bad and, this code may appear. 

Poor connection or bad wiring – Read the page ‘How to troubleshoot drivability issues’. Over time the pins in the connectors corrode/oxidize. Be sure to check the wiring and connections between the battery, power module, and logic module (or SMEC).  Fusible links from the battery should also be checked to be sure they are making good connection. 

For turbocharged engines, codes 26 and 27 are related to the injector driver circuits. Code 26 is related to injector driver circuit 1, and indicates that the injector circuit is either open or shorted.  The Power Limited light will not be lit and the system will not enter limp mode.

For Throttle Body Injector (TBI) — single fuel injector systems, the most common 2.2 and 2.5 engine systems —  code 26 is thrown when peak injector current is not reached.  

Poor wiring or connection - Read the page ‘How to troubleshoot drivability issues’. Check the wiring and connections from the logic module to injectors #1 and #2 for Turbo engines.   Check the harness from the TBI injector to the computer. Clean and re-grease the connectors with dielectric grease.

Injector driver transistor failure (turbo engines) – When the injector driver is working properly the signal the voltage to the injector should jump to 12vdc when injector is on and drop to 0vdc when injector is on. These signals can be measured from the power module (or SMEC).  If you don’t see these voltages at the harness where it connects to the injector ‘and’ you have insured that the harness is good from the injector connector to the power module (or SMEC) then the power module should be replaced.

Injector failure (TBI engine) – Check the resistance of the injector. If it is too high or if it is zero ohms (an open circuit), the injector must be replaced.

Original is at Chrysler Fault Code 26: Injector issues http://www.allpar.com/fix/codes/faults/code-26.html#ixzz2bFFLbfmX 
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