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Misfiring and codes P0300, P0113, P0102, P0301 P0302, P0303, P0305 and P0306

Tiny
RICH NORBY
  • MEMBER
  • 2006 LEXUS RX 400H
  • 3.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 153,000 MILES
A rodent chewed off green wire to fuel injector connection cylinder 6. Also chewed insulation off both wires to cylinder 2. I replaced connector to injector 6 and repaired wires to cylinder 2. I started the engine and it is running very rough and knocking. Car ran perfectly before the chewed wires. Could it have messed up timing or be a computer issue? I have intake manifold off and checked for any more chewed wires. Replacing plugs while manifold is off. I had spark on cylinders 2, 4 and 6 still need to check 1, 3 and 5. This vehicle listed above AWD vehicle. I really could use help with any suggestions. Thank you, Rich Norby
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Sunday, November 29th, 2020 AT 11:17 PM

15 Replies

Tiny
KASEKENNY
  • MECHANIC
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I attached the testing for the P0113. I think that will lead you to your issue. I suspect you have more chewed wires that you are just not finding. This would not cause a timing issue or any other mechanical issue so this is almost guaranteed to be more wiring issues.

Unfortunately these are not easy as you never know which wires they chewed on. So we just need to start somewhere and fix one thing and then keep going if that doesn't fix the other issues.

So I attached the testing for the intake air temp code because this is pointing to a wiring issues in the 5 volt reference wire. I would go through this testing and see what turns up.

Once you get rid of this code we will need to recheck what other codes are still there if any.

Here are some guides that will help with this:

https://www.2carpros.com/articles/how-to-check-wiring

The testing as the wiring information that you will need. However, here is another guide on using a volt meter if you need it:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Let us know what you find. Thanks
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Tuesday, December 1st, 2020 AT 2:01 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
Thank you for your reply, I will definitely check out the MAF sensor circuit. My daughter had to drive the car for about 10 miles to get it home at low speed due to the misfiring. Could that have caused the injectors to foul and set off codes for other cylinders misfire?
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Wednesday, December 2nd, 2020 AT 8:47 AM
Tiny
KASEKENNY
  • MECHANIC
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No. I don't think that caused any issue. I would just chase that other info on the P0113 and see what turns up. Let us know if you have other questions or how you make out.
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Thursday, December 3rd, 2020 AT 12:13 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
I cleaned the MAF sensor, installed new plugs and fuel injectors. Codes PO113, PO303,305,306 cleared. I still have codes PO301, PO302 and 7E8 control module engine. I'm going to start on cylinder #2 plug and coil to see if they have spark. The engine is running rough and engine light is on. I can't find what code 7E8 is for. Also code 7EA came up but reads no memory stored. I'm sending a picture of the freeze frame just in case it is helpful. Again any guidance and suggestions will be greatly appreciated. Thanks, Rich
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Thursday, December 10th, 2020 AT 12:42 PM
Tiny
KASEKENNY
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Does that say negative 20 on the short term for bank 2? If it does then you have either a sticking injector on that side or a spark plug not firing. Basically it is saying that you don't have enough oxygen in the exhaust and it makes the assumption that this is because there is too much fuel which is throwing off the ratio.

Just confirm that for me and then I think you have the right plan to just tackle cylinder 2 misfire and then go from there.
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Thursday, December 10th, 2020 AT 7:08 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
The short term bank 2 is + 20.3, sorry for the extra dash. Is the +20.3 okay? I pulled plug # 2 and it was dry, then I layered it with coil on engine and started engine briefly and saw spark. I checked fuel injector on cylinder 2 and have 11.47 volts going to it. I installed new injectors but didn't test them first, not sure of voltage to use. Would 12v be okay? I'll need to remove intake manifold again to check cylinder number 1 plug and injector bummer. Can you get me a link to wire diagrams so I can check wires back to ECM. Thanks I appreciate your help.
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Friday, December 11th, 2020 AT 8:48 AM
Tiny
KASEKENNY
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Okay. That helps. +20 is not good either. That just shows it is going the other way where the sensor is showing high oxygen content which means there is low fuel. So that would point to an air leak allowing too much air in (unlikely to effect just one cylinder) or the injector is not firing the proper amount of fuel. This could be due to a faulty injector or the ECM is not firing it.

Here is a guide on how to test an injector:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

You are correct that they should have 12 volts but they have 12 volts all the time. The ECM supplies the ground which causing the injector to open.

I included the wiring diagram and the ECM pin out showing where these wires are. Let's test them using a test light as shown in the link or use a noid light. If the test light or noid light is lighting up then the ECM is grounding the injector correctly. Thanks
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Friday, December 11th, 2020 AT 6:21 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
Thank you for the ECM wiring diagrams, I was able to get to injector #1 and test for pulse as well as #2 4 6 without removing intake manifold. I have no pulse on #2 injector. I did a continuity test back to ECM plug and the wires checked good. Would this indicate that the switch that controls the ground side of the circuit is bad and I need to change the ECM? If that is the case could you suggest my next step as far as finding another one and programming issues. Thank You
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Monday, December 14th, 2020 AT 5:05 PM
Tiny
KASEKENNY
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Okay. If the injector is not firing but the others are and the wiring is okay then that would be an ECM issue. As for finding the part, I would just do an internet search as I am sure you can find a company that sells them already programmed. Even though this is a Lexus, it has Toyota software and they are pretty common to find already programmed so that you just have to install it.
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Tuesday, December 15th, 2020 AT 6:11 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
Thanks for your help! I think I figured out by using the diagrams you provided that the code 7E8 control module is terminal 7 on plug E8 at the engine control module. Terminal 7 is the ground for the pulse to the injectors. It looks like the switch that provides the pulse is not working. I don't think it's repairable. Thanks again I don't think I would have gotten this far without your help. I'll keep you updated.
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Tuesday, December 15th, 2020 AT 7:34 PM
Tiny
KASEKENNY
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You are more then welcome. That is great info. Thanks for the update and using 2CarPros. Please come back next time.
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Wednesday, December 16th, 2020 AT 5:03 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
I have a question concerning the wiring from the ECM to the fuel injectors. I'm trying to test the wires from injector plug to ECM plug with both ends disconnected. I tested pins 1 thru 7 on ECM end plug and all 7 pins ran to ground. I can't see from the schematic you sent me on fuel injectors. Why I'm reading to ground? I can't find schematics to show what else may be connected to allow this. I've purchased a replacement ECM, but I'm concerned about it being damaged if there is a problem. If you have any schematics that may show the path it would really help. Or if you have any other information or suggestions on how I can test for short to ground.
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Tuesday, December 22nd, 2020 AT 5:25 PM
Tiny
KASEKENNY
  • MECHANIC
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The wiring diagrams that I provided above are the complete circuit from the injector to the ECM.

It is just a straight shot from injector to ECM. I am not sure if I am understanding how you are testing these but let me explain how they work and then you tell me if that makes your testing make more sense.

The injector is provided 12 volts on the red wire at all times the key is on. Then when the ECM wants to fire the injector it grounds the circuit on the other wire and the circuit is completed and the injector opens.

So in other words, it is an open circuit until the ECM wants to open the injector and the ECM provides the ground and the injector fires. So if you are testing the wire from the injector to the ECM for a short to ground. You should have ground if the injector is opening.

However, if you have disconnecting the injector and ECM and testing just the wire and you have a short to ground then you have a wiring issue.

If you have the ECM still plugged in and you are testing for a short to ground with just the key on and you have ground then the ECM is grounding the injector when it should not.

Let me know if I am misunderstanding something. Thanks
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Wednesday, December 23rd, 2020 AT 6:16 PM
Tiny
RICH NORBY
  • MEMBER
  • 30 POSTS
Thank you KASEKENNY1, with your help I was able to trace the problem with my Lexus 400h back to the engine control module. I replaced it with a used one, had it reprogrammed and now have the car back on the road. The wiring diagrams you provided any guidance along the way is greatly appreciated. Keep up the great work.
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Saturday, January 16th, 2021 AT 8:25 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Thank you so much. Good work and thank you for the update. That is great info that will surely help others that visit this page. We love it not only when you repair the vehicle but then tell us what it was so that others will benefit from it as well.

Thanks for using 2CarPros.
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Saturday, January 16th, 2021 AT 5:42 PM

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