How to make a F23A5 work where a F23A4 was

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05-25-2022, 08:58 AM

newmotorgb

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Join Date: May 2022

Posts: 4

How to make a F23A5 work where a F23A4 was

Hi, hoping for some help. Customer told us he had a 2002 Accord non-vtec so we ordered him the non-vtec engine for that which was the F23A5. We had a new tech here install the engine and he didn't look or realize the customer actually had a vtec F23A4 engine coming out. After the new engine F23A5 engine was installed the customer keeps getting PO1259 vtec code and rough running at times. We looked a little into it and realized that the cam and rockers are different in the head. To the best of our knowledge that was the only difference. The holes for the vtec solenoid were there. Thinking that was the only difference we took the cam and lifters from the F23A4 head and installed it into the F23A5 head/engine in the vehicle. After driving for a while the same code PO1259 still comes back. Tried a new vtec solenoid and oil switch and it doesn't make a difference.
Can anyone tell us what else can be different from the non-vtec to vtec engines that may cause this code. What are we missing and can this be modified somehow? Thank you very much.

05-25-2022, 04:49 PM

PAhonda

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Join Date: Sep 2006

Location: Houston, TX

Posts: 15,647

I was looking through the shop manual to troubleshoot a P1259. Step one is to do the ECM/PCM reset procedure. If you have a scanner that can do the relearn procedure, give it a shot.

05-25-2022, 05:13 PM

newmotorgb

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Join Date: May 2022

Posts: 4

Quote:

Originally Posted by PAhonda

I was looking through the shop manual to troubleshoot a P1259. Step one is to do the ECM/PCM reset procedure. If you have a scanner that can do the relearn procedure, give it a shot.

I had no idea there was a relearn available for this. I'll look into this tomorrow. Thank you.

05-26-2022, 07:16 AM

newmotorgb

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Join Date: May 2022

Posts: 4

Quote:

Originally Posted by newmotorgb

I had no idea there was a relearn available for this. I'll look into this tomorrow. Thank you.

Actually found out my tech did that already many times with no help. Any other thoughts? Thank you

05-26-2022, 01:54 PM

redbull-1

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Join Date: Oct 2010

Location: United States

Posts: 7,085

See post #6 in this thread regarding the oil control orifice which needs to be removed. The P1259 is likely due to the oil pressure not sufficient at the VTEC oil pressure switch.

https://www.hondaaccordforum.com/for...me-swap-57618/