P0300 but no check engine light - S-10 Forum
 
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post #1 of 6 Old 05-14-2019, 08:14 PM Thread Starter
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P0300 but no check engine light

Today I took my truck to Advance Auto so I could have the kid there scan its codes for me and reveal what's wrong with my ABS. The short answer is, everything, but that's a topic for another thread (or possibly several threads). The thing that really scared me was his scanner also showed I was getting a p0300 code, indicating a random misfire. I haven't noticed any misfiring, and like the subject says, the check engine light hasn't come on. My own scanner shows no codes, which confuses me.

This truck has not run better in the entire time I've owned it, due to recently unclogging my cat and fixing some other performance issues. How do I determine if this p0300 is really an issue? My next move was going to be replacing the distributor cap, as I have already swapped on a different ICM. Truck has new plugs and wires. Is there anything else I should be looking into?


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post #2 of 6 Old 05-14-2019, 11:28 PM
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Re: P0300 but no check engine light

If your own scanner shows no codes I'd trust that. Not saying AA would alter their scanner to show a p0300 on every car, but it would help sell a lot of tune up parts.
What did you get for ABS codes?
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post #3 of 6 Old 05-15-2019, 08:46 AM Thread Starter
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Re: P0300 but no check engine light

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Originally Posted by oldeerslayer View Post
If your own scanner shows no codes I'd trust that. Not saying AA would alter their scanner to show a p0300 on every car, but it would help sell a lot of tune up parts.
This truck came with a new distributor cap that hadn't been installed, so I'll probably put that in anyway and keep an eye on it. I was under the impression that tripping an ECM code like that would cause MIL illumination.


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Originally Posted by oldeerslayer View Post
What did you get for ABS codes?
C0225 - Left front speed sensor shorted
C0222 - Right front speed signal missing
C0265 - Electronic brake control module motor relay circuit
C0227 - Left front wheel speed signal erratic
C0236 - Rear wheel speed sensor signal missing
C0226 - Left front speed sensor missing

So, big trouble with the left front, apparently. And the right, and back, and the EBCM. I might start with the EBCM first and see if its grounded properly.

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post #4 of 6 Old 05-15-2019, 01:44 PM
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Re: P0300 but no check engine light

Sounds like a good place to start since apparently nothing is working on your ABS. Look over the wiring and connectors for damage or corrosion around the pump area. Have you tested the 60A ABS fuse in the UBEC?

Unless the distributor cap is an original equipment quality replacement I'd skip it. S10's are funny about ignition parts. They seem to only be happy with what they were built with. That goes for plugs and wires also. Maybe that is causing an occasional misfire. That code has a threshold of a certain number of misses before lighting the SES bulb.
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post #5 of 6 Old 05-15-2019, 04:12 PM
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Re: P0300 but no check engine light

ok- first things first- CLEAR the codes in the computer and clear the ABS codes- then describe WHAT your ABS is doing besides the light being on- old codes suck unless they are set while you are watching.- you have codes that usually wont set together- LF shorted,LF erratic,LF missing

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post #6 of 6 Old 05-15-2019, 08:02 PM Thread Starter
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Re: P0300 but no check engine light

Quote:
Originally Posted by oldeerslayer View Post
Sounds like a good place to start since apparently nothing is working on your ABS. Look over the wiring and connectors for damage or corrosion around the pump area. Have you tested the 60A ABS fuse in the UBEC?

Unless the distributor cap is an original equipment quality replacement I'd skip it. S10's are funny about ignition parts. They seem to only be happy with what they were built with. That goes for plugs and wires also. Maybe that is causing an occasional misfire. That code has a threshold of a certain number of misses before lighting the SES bulb.
I don't think the one on there was original, because it was white and I've only seen black on the ones I've owned and picked apart at the yard. I got it off and found it looked like crap on the inside. All the little metal posts were worn and covered with a white residue. I also tried to change the rotor, but found the one from my extra engine got broken when the guy I paid to move it for me dropped the motor on the ground. Then he had the nerve to ask for a tip. I said here's a tip: If someone pays you to move an engine, DON'T DROP IT!

So after I put the first rotor back in, everything fired up and the truck runs even better. I'm cautiously optimistic that the cruddy old distributor was causing that misfire. Here is new vs old:

https://www.s10forum.com/forum/attac...316805&thumb=1

Quote:
Originally Posted by Jayhawke View Post
ok- first things first- CLEAR the codes in the computer and clear the ABS codes- then describe WHAT your ABS is doing besides the light being on- old codes suck unless they are set while you are watching.- you have codes that usually wont set together- LF shorted,LF erratic,LF missing
Besides the codes, seems like it's stopping fine. Even really short stops, like when the traffic here suddenly goes from flowing at 80 mph to 5 mph and I'm forced to slam on brakes. No skidding and no mushy pedal. Pedal feels fine. Perfect travel on the pedal from floor to return position. Basically, if the lights weren't on I wouldn't notice a problem.

I have noticed the e-brake is sometimes a bit slow to disengage. But that's probably just a stretched out cable.
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