Mysterious code 6 - Cb9 Accord

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frijoles
Posts: 14
Joined: Mon Apr 03, 2023 6:49 pm

Mysterious code 6 - Cb9 Accord

Post by frijoles »

Hey guys, I hope this is the right place to post this question. I will try to summarize what I've done as best as possible.

I have a 93 and a 91 Accord Wagon. In the 93 Accord, it was my original car, with an H23A swap that I could never get running perfectly. It had some issues with water getting into the cabin and causing weird wiring issues. I bought the 91 Wagon to swap all my parts over to, because I couldn't figure out the issue. This was between 5-8 years ago. Recently I decided to actually do the swap, so I did the engine swap, wiring, swapped over all the parts, added a wideband o2, etc. Now, right before this, I did get the engine running in the 93, but again, it wasn't "right". I decided to go through with the swap for a few reasons, one the water pump was bad, two, the engine mounts were bad because of the hackjob the manual swap was in the chassis.

So, anyways, back to now, car wired, new s300, wideband, etc. Car won't start on a basemap. It will, sort of start, immediately sputter and die. And also have a code 6 for ECT and code 21 for VTEC spool. I assumed this was a wiring issue, so the first thing I do is UNDO all the wiring I modified. Removed VTEC, wideband, etc. Code remains. This code shows up on ignition on, engine off, instantly. If I clear codes it comes back immediately. I've found a few threads on this, and most people say, "I'm trying a new ecu tomorrow" and then don't reply, so I assume that's usually the problem. So I replaced the ECU, still had the issue. Assumed now that the s300 board was the issue, so I tested it in another car AND bought a new working s300. Of course the board I had was fine. The ECU was fine. So I replaced the entire cabin wiring harness that I had on hand. So now it's a fully manual wiring harness, no modification needed for that. I didn't damage, or cut, any wires. I did not do anything at all to the harness, totally virgin wiring harness. New virgin engine wiring harness, only deloomed to reach the plugs that it needs to reach. No anything added for VTEC yet, or the wideband. I haven't tried to even start the car yet, but STILL the code 6 remains as soon as the ECU gets power. I've checked my grounds and plugs, I don't even know where else to look. Not exactly sure what specific wires I should check for continuity now.

Any help would be greatly appreciated, if you can just point me in the right direction I would be so grateful.
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Spunkster
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Re: Mysterious code 6 - Cb9 Accord

Post by Spunkster »

Try the ECU on a known working vehicle
frijoles
Posts: 14
Joined: Mon Apr 03, 2023 6:49 pm

Re: Mysterious code 6 - Cb9 Accord

Post by frijoles »

so I tested it in another car AND bought a new working s300.
Been tested in another car. Been tested on an engine simulator. Also have two more ECUs now that all do the same thing. Only get a code 6 on this specific car.
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Spunkster
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Re: Mysterious code 6 - Cb9 Accord

Post by Spunkster »

It sounds like the ECU is damaged that is getting the ECT code and would need to be replaced.
frijoles
Posts: 14
Joined: Mon Apr 03, 2023 6:49 pm

Re: Mysterious code 6 - Cb9 Accord

Post by frijoles »

Yeah, I thought the same thing. That's why I got a second s300 and it gives the exact same issue, down to the exact same coolant temperature reading when the engine is off. One s300 I tried in two different ECUs, the other s300 I just got last week already installed into a p28 and it gives the exact same issue. I also had the first one shipped off and tested, and it was shown to be fully functional.
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Spunkster
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Location: Hondata

Re: Mysterious code 6 - Cb9 Accord

Post by Spunkster »

If it only does this on this specific vehicle, then there must be an issue with the wiring or sensors in this vehicle.
frijoles
Posts: 14
Joined: Mon Apr 03, 2023 6:49 pm

Re: Mysterious code 6 - Cb9 Accord

Post by frijoles »

I feel so stupid, so stupid I almost don't want to post a reply. But I will. I read the Honda wiring diagrams wrong. I read my electrical manual wrong. I made assumptions that I shouldn't have, with the issue staring me in the face the whole time.

I never plugged the damn sensor in.

Technically, I plugged both the ECT and fan switch into fan switch plugs. The ECT plug sat there unused. It wasn't until I talked to someone that explained I should ignore those in the wiring diagram that I realized what I did, and that's what my issue was. I did the same thing on both wiring harnesses that I made, because I went with those wrong assumptions.

Never assume anything, guys.

But at least it's fixed now!
KellieWallace
Posts: 1
Joined: Thu Jul 27, 2023 3:27 am

Re: Mysterious code 6 - Cb9 Accord

Post by KellieWallace »

frijoles wrote: Thu May 04, 2023 5:57 am Hey guys, I hope this is the right place to post this question. I will try to summarize what I've done as best as possible.

I have a 93 and a 91 Accord Wagon. In the 93 Accord, it was my original car, with an H23A swap that I could never get running perfectly. It had some issues with water getting into the cabin and causing weird wiring issues. I bought the 91 Wagon to swap all my parts over to, because I couldn't figure out the issue. This was between 5-8 years ago. Recently I decided to actually do the swap, so I did the engine swap, wiring, swapped over all the parts, added a wideband o2, etc. Now, right before this, I did get the engine running in the 93, but again, it wasn't "right". I decided to go through with the swap for a few reasons, one the water pump was bad, two, the engine mounts were bad because of the hackjob the manual swap was in the chassis.

So, anyways, back to now, car wired, new s300, wideband, etc. Car won't start on a basemap. It will, sort of start, immediately sputter and die. And also have a code 6 for ECT and code 21 for VTEC spool. I assumed this was a wiring issue, so the first thing I do is UNDO all the wiring I modified. Removed VTEC, wideband, etc. Code remains. This code shows up on ignition on, engine off, instantly. If I clear codes it comes back immediately. I've found a few threads on this, and most people say, "I'm trying a new ecu tomorrow" and then don't reply, so I assume that's usually the problem. So I replaced the ECU, still had the issue. Assumed now that the s300 board was the issue, so I tested it in another car AND bought a new working s300. Of course the board I had was fine. The ECU was fine. So I replaced the entire cabin wiring harness that I had on hand. So now it's a fully manual wiring harness, no modification needed for that. I didn't damage, or cut, any wires. I did not do anything at all to the harness, totally virgin wiring harness. New virgin engine wiring harness, only deloomed to reach the plugs that it needs to reach. No anything added for VTEC yet, or the wideband. I haven't tried to even start the car yet, but STILL the code 6 remains as soon as the ECU gets power. I've checked my grounds and plugs, I don't even know where else to look. Not exactly sure what specific wires I should check for continuity now.
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Any help would be greatly appreciated, if you can just point me in the right direction I would be so grateful.
Please double check the connection of sensors and power supplies, see if the root cause can be found.
tracyberge
Posts: 1
Joined: Fri Sep 29, 2023 12:46 am

Re: Mysterious code 6 - Cb9 Accord

Post by tracyberge »

The ECT sensor is responsible for providing temperature information to the ECU. A faulty sensor or a wiring issue related to the ECT sensor could cause code 6 to appear. Make sure the sensor is connected properly, and consider testing or replacing it if necessary.
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