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Go To PIDs for Diagnosing Electric Vehicles

It is no secret that one must be able to not only interpret the information that the PIDS provides for us but must also know which PIDS to look at to aid in diagnosing various complaints. Often, we will secure a suspicion based off of symptoms or PID deciphering, and then we will back up our diagnostic suspicions by looking at other similar PIDS to ensure we are on the correct diagnostic pathway.


On an ICE engine, I typically use just 6-main PIDS to determine what is ailing the vehicle. On an electric vehicle, however, I find that I need to broaden my scope of perception and look at more PIDS to determine the fault of the vehicle. In this article, we will not only identify those PIDS but also explain what it is that I use these PIDS for. These PIDS are my go-to PIDS for all-electric drive types of vehicles, both Hybrid and full electric.


 

Temperature-related PIDS:

Keep in mind that there is a great deal of scan tool PIDS that we often won’t really need to use when diagnosing faults. The electric drive type of vehicle is no exception to this. Basically, we will be interfacing the powertrain control module, the high voltage module, the transmission module, and the air conditioning module for most of our diagnostic procedures when dealing with a hybrid or electric drive vehicle fault. The following are some of my favorite PIDS found within these systems and why I use them.

Since heat is a byproduct of electricity, the manufacturer pays very close attention to heat within every aspect of the high-voltage system. There are literally over 50 different temperature-related PIDS found within the various modules. I use the heat-related PIDS to determine if there is an over fault like a short, which may be drawing too many amps thus increasing the temperature, I use them to help determine if the cooling functions are correctly working such as the electric water pump for the inverter/converters and the motor generators or the air blower circuits inside the battery packs. Many faults can be found with just this one input alone from cooling system issues and air flow concerns all the way to hard electrical faults. Obviously one can use bi-directional tests such as activating pumps and blowers and watching the perspective temperature PIDS to see if the overall temperatures respond accordingly.

 

Torque-related PIDS:

While scanning the transmission-related PIDS, I often use the desired and actual torque-related PIDS for insight as to the status of the motor generators. If I find the desired isn’t matching the actual values, I will for sure want to perform the tests on the stator windings we discussed earlier in this manual. I also use these PIDS for insight regarding the dual mass flywheels.


 

MG Phase-related PIDS:

These can be found within the transmission module as well. Remember, the 3-phase windings of the stator assemblies should be 120 degrees apart. Most of the time this will never change (see the earlier section regarding magnetism and North and South Poles), I have seen however that when excessive amperage is being emitted from the MG windings, this usually indicates a shorted winding or harness and will cause the 3-phase to become out of sync.


 

Inverter Radiator Temp PID:

I use this PID to help locate HV cooling system-related issues from external leaks to restrictions and even faulty electric circulating pumps


 

Other Radiator PIDS: (vehicles with more than one cooling system)

I use this PID to help locate HV cooling system-related issues from external leaks to restrictions and even faulty electric circulating pumps


 

System Amperage-related PIDS:

This is a quick go or no go pid to give me an insight if the electronics are working as they should. Too high of amperage usually indicates a lack of resistance of some sort within the hv circuitry, too low would indicate an excessive amount of resistance. This is a go, or no-go test for me because if i find an issue with the amperage, then the real work begins by having to interpret the other PIDS to try and determine where the issues lie.

 

Engine Run Command PID: (Hybrid Only)

This is one of my first go-to PIDS I look at if the HV battery's overall state of charge is low. If I see the ICE is commanded on but it’s not running, then I need to determine the cause of this problem. I also can use this for even testing the pedal position sensors by depressing the pedal rapidly a few times and this should cause the engine to start!


 

Inverter Resistance Block PIDS:

These are the PIDS that refer to the resistors found within the inverter assembly, which are responsible for draining the capacitors. If you notice the capacitors are holding a charge longer than expected, be sure to check these PIDS. You will most likely find a bad resistor or two.



 

A/C Compressor Commanded State and Pressures PIDS:

I use these PIDS anytime I’m dealing with an air conditioning system complaint. I can get an overall idea while sitting in the driver’s seat of what the problem may be. If the A/C system isn’t cooling first, I’ll see what the commanded state of the HV compressor is. It should be on, if it's not I will be searching for an electrical fault. If it is commanded on, I will look at the pressures to see if I may be dealing with a low-charge issue. If the pressure is low and the A/C compressor is running, I know I will be dealing with some sort of leak in the system.



 

Contactor PIDS:

These related PIDS are important in the overall scheme of the HV circuit. Remember, these contactors must close for the HV system to wake up!



 

Battery State of Charge PID:

This is an invaluable PID to view. This is an overall health check of the entire HV electrical system. It is imperative to view this PID for insight into the health of the HV battery pack. Great for used car purchase scans.



 

Battery Block PIDS:

These PIDS should be scanned to see how well-balanced the HV battery assembly is. They also will give you great insight as to which cells may be having an issue so you can then perform specific pinpoint tests on those suspicious cells. Remember to test open circuit voltages of the cells as well as loaded voltage tests.



 

Lowest and Highest Block PIDS:

These two PIDS alone will tell you if the battery is balanced. The specification for an out-of-balance battery is very low (under 500 mv). If the battery is out of balance, you will not only set DTCs, which may even give a triangle of death, but you definitely have weak or failing cells!



 

Boost Percentage PID:

This PID is used to determine if the boost circuitry is working properly. While power braking or graphing this PID while driving, we should see this percentage go between 50-85% while accelerating from a stop. If this isn’t occurring, we would need to perform pinpoint tests on the boost components within the inverter assembly.



 

Control Pilot PID (Control Pilot)

This PID allows one to test the communication circuit between a charger and a vehicle



 

Proximity PID:

This Pid allows one to test that the vehicle can recognize that a charging cable has been plugged into the vehicle



 

Charging PIDS L1/L2 and Overall:

These PIDS allow one to test that the charger is working as designed and delivering charging current to the vehicle.



 

KW Charging PID:

This PID allows one to check and verify that the charger is delivering to the vehicle and that the BMS is regulating the correct KWH as designed.


By: John Forro “Electron-John”

Autel Instructor

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