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Error Code P1604 – Symptoms, Causes and Solutions

In modern cars, it is the software-controlled electronics that play a very important role in the operation of the various subsystems of the vehicle. There are many control modules installed that are responsible for the operation of the brakes, engine, transmission, steering, audio, and other systems.

Although all these controllers work on their own, they are connected through some communication protocols. Error Code P1604


The IPC (instrument panel) It can be described as one of the few devices with which the vehicle communicates with the driver. Devices such as the display screen and information center are considered additional devices for the IPC or subsystems.

Although the instrument panel is simpler than other controls, it is extremely important because it is one of the few that the driver sees. It takes signals from various sensors and communicates with most of the vehicle modules to obtain relevant information and its status.

What does code P1604 TOYOTA mean?

He code P1604 It is stored if the engine does not start or continues not to start for a certain period of time. The P1604 code is also stored if the vehicle has run out of fuel. It is necessary to check if there is enough fuel in the tank before carrying out this inspection.

Reads: Error Code P1320 – Ignition Coil and Power Transistor

When the vehicle engine runs at more than 500 RPM for more than 10 continuous seconds, the PCM (Power Train Control Module) establishes communication with the instrument panel if a serial data signal is found, which turns out to be invalid or no serial data is received, the P1604 OBDII fault code will be set.

Symptoms of fault code P1604 Generic

  • The Check Engine light comes on.
  • Invalid data is displayed on the instrument panel.

Causes of the P1604 Generic OBD2 fault code

The causes of the P1604 OBD2 diagnostic code being established are:

  • The electrical circuits of the IPC may have damage to your cables.
  • The electrical connections in the instrument panel may have deficiencies that could cause a short circuit.
  • The CPI may be in bad shape.

Possible solutions for DTC code P1604 Generic

The steps to fix DTC code P1604 OBDII are as follows:

  • See Technical Service Bulletins.
  • With the help of the electrical diagrams, locate all the wiring in the instrument panel. Look for corrosion or burn damage. Repair what is necessary.
  • Measure the voltage of the circuit that controls the IPC and verify that these readings match those specified by the manufacturer. If any condition is detected that causes a short circuit, make the appropriate repairs.

Questions and answers

Ask: I have a 2006 PT Cruiser, Touring Edition. The check engine light came on about a month ago and I finally got around to checking it last weekend. I haven’t noticed the car running any differently since the light came on. Here is the letter from the Goodyear Service Center that diagnosed the problem:

“We got 2 codes from the vehicle, P01603 and P01604. We suggested cleaning the battery terminals because they had a lot of acid corrosion buildup. After showing the customer and doing the service, we got the codes P01604*2 and 2 transmission control codes. We rebooted the system again and got a computer link issue where the PCM is not communicating with the scan tool. “We believe the PCM is failing and will eventually fail completely.”

They want to replace the PCM at a cost of around $800. Does the diagnosis sound legitimate? Yes that’s how it is, Can I replace the PCM myself? Is it difficult to get to and requires specialized tools to remove and install?

It has been running fine since I got it back, but the check engine light is still on. I live in California and my concern is that if I leave it as is it may not pass the smog test when it comes time for that annual test.

Thank you

Answer: Error code P01604

I have extracted the code according to your instructions and it actually came out P1604. My wife has a friend whose husband is the service manager at a Toyota dealership and she recommended Disconnecting the negative and positive battery cables and then short-circuiting them for a minute or two.

He said that there is a capacitor that can still provide power to the PCM and you want to drain this power. Then leave it unplugged for 5 minutes as he suggested. By doing this, he said it will totally shut down the PCM, so when you reconnect the battery cables and start the car again, it will be like a hard reset of the PCM.

He said it can malfunction a little at first as the system relearns how to idle and perform other functions. That probably explains why the Goodyear dealer got the 2 transmission control codes after resetting as I mentioned above. If still code P1604 you will need to replace the PCM.

I found a site that sells used PCMs (http://www.allcomputerresources.com/). You send them your VIN and mileage and they pre-program (flash) the unit and send it to me. The price on their eBay store is $169- which is lower than their website price of $199. How difficult is it to change the PCM myself? Do I need any special tools?

Thank you

Answer: P01604 Error code

Well, I did what my friend recommended. He recommended I disconnect the negative and positive battery cables and then short them for a minute or two. He said that there is a capacitor that can still provide power to the PCM and he wants to drain this power.

Then leave offline for 5 minutes as you suggested. By doing this she said it will turn off the PCM completely. I tried the procedure twice and still had the same error code.

Now the mechanic I went to that I mentioned above said I needed a new PCM. The P1604 error code appears on this site as “P1604 Loss of IPC Serial Data” (Error Codes). Is the problem really the PCM? I hate buying a new one if it’s not.

If you want to know other articles similar to P1604 OBD2 Error Code you can visit the category Fault Codes.


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