Hello everyone, I'm having a persistent issue that is driving me completely mad. My CEL is on and throwing error code 21 (Vtec Solenoid). Well I took it to someone who hooked it up to a computer and they said the computer was showing them that code 21 is VTEC Solenoid and that the computer was telling them it was something electrical. I just went ahead and replaced the Vtec Solenoid and spool Valve assembly and yet the error still persists. I then took it to another mechanic than ran a diagnostic on my car, I believe a electrical diagnostic and he said that it was showing him my ECU is bad, although my car seems to run fine besides that stupid CEL. I'm trying to find out the best way to test the wire from my solenoid to my ECU or test the ECU itself. There is all sorts of electrical tape holding bunches of wires together from previous owners so it will be extremely hard to visually inspect the length of the wire in hopes of seeing a bad spot. Is there any way to check the wire with a multimeter perhaps? Any help would be greatly appreciated...this problem has been going on for over a year and my car sooooo needs its inspection sticker lol.

 

Also if I just buy a used ECU from like ebay or a scrapyard, will I need to have it programmed in order to work in my car, even if the part numbers are identical?

 

You need an ECU from a 94 or 95 accord EX. The ECU also needs to come from a car with the same transmission as yours. There is no programming necessary on the 94, that didn't start until the 98 accords.

One way to test the wire is to measure the resistance at the vtec solenoid to ground, then plug in the electrical connector and measure the resistance to ground at ECU for that wire. The common diy thread on top of the gen tech help forum has a link for shop manuals and you can get a pdf of the 94 manual for free via the hondatech link.

 

Should be pin A4 on the ecu that is the vtec connection. As PA said test it, with your "story" about the condition of the wires, I'd suggest a continuity test from the vtec to A4 as well......want to be sure that wire isn't broken somewhere.

 

Normally when an ecu goes bad it will have burned spots inside of it. You can pull the ecu and take a look inside.