Power loss, codes are not stored and unable to be read

DEANO1961

MEMBER
1997 TOYOTA TACOMA
2.4L
4 CYL
2WD
MANUAL
196,000 MILES

When the check engine light comes on the engine idles fine, the A/C compressor stops working, and there is a loss of power when trying to accelerate. When the check engine light is off everything is fine. The check engine light is intermittent and has only come on after the truck is warm. The truck does not run hot. Codes are not stored and unable to be read with quality readers at a reputable repair shop. Please let me know if you had this issue and found a solution. Thanks

7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

This could be a couple things but we need to start with checking the battery and alternator. This sounds like load shedding. So it sounds like the alternator is coming and going and when it is not charging the battery drains and the ECM starts shutting things off to try and keep the voltage up.

Here are some guides that help with these different issues:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/car-battery-load-test

https://www.2carpros.com/articles/symptoms-of-low-engine-power

Also, this would make sense why there are no codes because it most likely is not turning the light on for a power train issue so it is not recording them. However, have you checked for codes when the light is on?

Let's start with checking the battery with a load test and then the alternator. Also I suspect we are going to have to check the alternator when this is acting up as when it is not it sounds like it is charging properly.

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Wednesday, March 24th, 2021 AT 6:08 PM

DEANO1961

MEMBER
5 POSTS

Hello KaseKenny1, and thanks for working with me.
I checked the battery without the truck running (12.7 V), at approximately 1,500 RPMs (13.9 V), at approximately 1,500 RPMs with lights and A/C on (14 V). I turned the lights on for approximately 15 minutes. Then started the truck and the bulbs only dim slightly and the truck started right up.

The check engine light came on again today and no code was detected by the reader when the check engine light was on.

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Saturday, March 27th, 2021 AT 6:00 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. The battery sounds like it is okay and can carry a load.

However, the light is on and no codes sounds odd. I am thinking that we have some OEM codes and they are not OBD II specific codes. So some code readers do not pick these up they only read those codes that are mandated by the federal government.

I would suggest stopping by a parts store and have them scan it with another reader and see if they turn anything up. This normally has to do with the emissions are higher then expected.

Let us know what you find.

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Sunday, March 28th, 2021 AT 6:09 PM

DEANO1961

MEMBER
5 POSTS

Hello KaseKenny1, I took it to a reputable repair shop that specializes in Toyotas, and they were unable to find any codes. They thought it might be the ECM. Thanks

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Sunday, April 4th, 2021 AT 3:44 AM

KASEKENNY

MECHANIC
18,907 POSTS

Wow. I am surprised. However, that is what I would suspect that this point as well. Basically the ECM is not setting any codes because it is the issue. This is not a definitive test but normally a check engine light with no codes is the ECM itself.

If it were me, I would replace it and go from there.