Chrysler circuit codes

Bruce Technician Spring Hill, Tennessee Posted   Latest  

So Chrysler, other manufacturers may do the same, circuit codes for injectors and solenoids monitor the voltage spike created when the solenoid or injector are turned off. But what is the threshold? About a month ago I had a 3.6 Challenger that had a P0302 and a P0202, but no current misfires. I compared the #2 injector to 1, 3 and 5. Bank 1 injectors were identical but #2 was about 3 volts less on the inductive kick. Don't remember exactly, but I think amperage was close to 1 amp on good injectors and closer to 0.5 amp and #2. #2 measured at around 30 ohms and the good injectors were around 15 ohms. 

From service information "Set Condition: The Powertrain Control Module (PCM) monitors the continuity of the injector circuits as well as the voltage spike created by the collapse of the magnetic field in the injector coil. Any condition that reduces the maximum current flow or the magnitude of the voltage spike can cause this DTC to set."

They don't provide any range. I replaced the #2 injector and I am confident that it is fixed. But what if the suspect injector was closer to the others? Does the PCM just compare it to the other injectors? Or is there a range that will cause the circuit code to set? 

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Michael Diagnostician
Holt, Michigan
Michael
 

That would be a interesting experiment. I would imagine they have a level they must meet though as a minor difference technically shouldnt cause much of a issue otherwise matching them would become absolutely necessary and would need to be sold in batches to match specs.

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Allan Instructor
Winnipeg, Manitoba
Allan
 

Bruce you don’t know what the voltage was when the PCM set the code or if the PCM set the code based on the inductive spike, it may have seen a circuit problem. The voltage was very close to the other injectors when you tested it but you also tested current draw as well as resistance to verify the injector was bad. That’s why we do multiple tests to verify a diagnosis. The DTC gave you a

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Allan Instructor
Winnipeg, Manitoba
Allan
 

Hey Bruce i just reread the code set criteria from your post. From service information "Set Condition: The Powertrain Control Module (PCM) monitors the continuity of the injector circuits as well as the voltage spike created by the collapse of the magnetic field in the injector coil. Any condition that reduces the maximum current flow or the magnitude of the voltage spike can cause this DTC to

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Dmitriy Analyst
Toronto, Ontario
Dmitriy
 

Hi Bruce, in modern injector drivers the inductive kick is shaved by a Zener diode. A partially failed injector may still shoot close to or above the Zener diode voltage, and it would be hard to notice the problem without analysing the other parts of the waveform and/or the turn-on current (the latter is done by the PCM, according to the Set Condition). The easiest thing to deal with this is

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Steve Instructor
Irvine, California
Steve
   

Bruce You did not specify the model year. On later models that monitor the Air/Fuel ratio Imbalance, Chrysler uses a number of strategies that monitor if the spark took place, and if the injector operated before it sets an imbalance code/misfire. Since you got a misfire code you went past the criteria for the imbalance right into the misfire. The nomenclature for Air/fuel ratio imbalance is

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