Hi, I'm new here and am hoping someone has experienced a similar problem that I am having or will have some suggestions of what else I can check or do.
About a month ago I got an ECL and pulled the code and found 16 Fuel Injectors. I bought and installed all new fuel injectors, since the car has about 250K+ miles and still have the 16 after replacing the FI's. I followed the diagnostics in the shop manual and listened to each FI with a stethoscope and hear the clicking in all four injectors as I should. The car starts and runs smooth like normal. I pulled the connector and measured approx 6.5 ohms on each of the injector resistors. I back probed the 4 injector signals coming into the ECU and got good battery voltage readings on all 4 pins.... A1, A2, A3,and A5. All connectors and pins look good. I recently replaced the PGM-FI master relay after having no start issues, but the DTC 16 persists after resetting the ECU. I'm running out of other things to try and wanted to check here to see if anyone has other ideas before buying another ECU, which I doubt will solve the problem. Thanks for any ideas in advance! Jim in Tucson

 

If this is a 4 cylinder Accord the injectors should only be reading 1.5 - 2.5Ohms as per the Honda shop manual. 6.5 is an odd number to get on any Honda injector. Low Impedance injectors are usually between 1.5 - 3 Ohm and high impedance are usually between 11 - 13 Ohms.

When you measured the resistance did you remove the injector clip and measure the resistance between the two pins on the injector or leave the clips on and back probe them? You should always remove the clips and go directly from the pins on the injectors.

 

I was referring to the injector resistors, not the resistance of the injectors. The injector resistors are supposed to read between 5 - 7 ohms and they all measured around 6.5 ohms.
I didn't measure resistance of the new injectors. I believe the DTC 16 is indicating the same problem I originally had before I replaced the injectors, which didn't clear the problem, so I have been looking for a different problem than the injectors, which are working fine like the old ones were. Releasing those clips while installed would be tricky, but might be necessary. I'll give that a go but don't think I will find a problem there, but I need to eliminate that as a possibility.
Thanks for your reply.

 

After checking the injectors you might want to crack open the ecu case and see if anything looks burned inside. This code is very uncommon.

 

Makes you almost wonder if it is a code 10 and a code 6

 

Absolutely. Good thought. OP, please recheck the code you're pulling. It's very likely not a code 16.

 

I pulled the cover off the ECU when I was back-probing the FI pins and everything looked fine on the back side of the main board, so I closed it up.

 

The first thing seen is a long single light, followed by 6 short blinks.... I think the 6 short blinks would come first if it were 6 + 10. There is then a long blank, followed by a long blink, then 6 short blinks. I've had several other codes, so I'm pretty sure this is a 16. I had a 1 + 8 + 14 + 16 before resetting the ECU after installing the new injectors.... I was left with 16 only after the ECU reset, which is what it was showing before I replaced the injectors.. From what you guys are saying about how uncommon this code is, it is sounding more likely the ECU has a problem, but I will go ahead and check the injector resistances when I get a chance. It starts and runs fine, so I doubt I will find any problem with the injectors, since I had this code before changing all of them with new and they are all clicking away and the engine starts and runs smooth. I was wondering if there might be a ground problem at the ECU in the A connector, so I pulled all three of the ECU connectors and put some dielectric grease on the power and ground pins, but it didn't help.

Looks like I will likely need to go ahead and buy another ECU and swap it out to see if the problem goes away. I'm concerned that they will fail the car at emission check next month, just because it has an ECL code... I doubt if they will pull the code on an OBD1, but don't know since the car has never had a code before during an emission test. I've thought about going ahead and letting them test it and see what happens, then buy an ECU if they fail it, since you have 30 days to retest it free, which would be plenty time to get a new ECU in there.

Thanks for your replies.... this is a head scratcher for sure.

 

Most emissions tests won't pass visual if the CEL is illuminated on the dash. Also they can hook up an OBD tool to check to see if the ECU has recently been reset. There are readiness codes that have to be confirmed in order to pass some emissions testing. Depends on the emission laws of your area.

When you said injector resistors, I thought you were referring to the resistance of the injectors themselves. Now I realize that you were referring to the resistor box found on the drivers side shock tower.

It is quite evident that you have the Honda shop manual and are following it to the letter, which is a good thing. So as you stated the next step would be to find a good ECU and swap it in.

 

he mentioned it was a 94 so it won't be able to be scanned

 

Thanks for your comments about how emission tests work related to CEL's. I agree with you and assume they will not pass the car with that big yellow light lit up on the dash, so I need to get if fixed within the next month for sure. Taking this to a dealer or repair shop would likely be very expensive, given the nature of this problem, so I need to try my best to find the problem. I am concerned with buying an ECU on eBay after seeing their warnings that the unit might require reprogramming..which would likely cost more than the unit, since it would need to be done at a Honda shop. I'm planning to call the local Honda service shop and ask if they have a way to test my ECU if I bring it in. If not, I'll ask if I could rent an ECU to use for testing, which I'm pretty sure I know the answer... If I strike out on both of those, I'll need to go ahead and buy an ECU to use for the testing and hope it works. If anyone has any advice or guidance on trusted sellers about buying used ECU's on eBay, I would appreciate hearing from you.

 

it shouldn't be too hard to find an ecu at the junkyard, it would need to be from a 94-95 ex though

 

Good idea. I'll makes some calls tomorrow. Thanks.

 

I've been thinking of alternate ways to check the FI resistances instead of removing those crazy spring clips and connectors. After studying the electrical diagram (attached), I plan to measure resistances from the ECU FI pins A1, A2, A3, A5 to the corresponding pins in the female pin side of the FI resistor box connector, With that connector open, I will be measuring resistance of each injector, plus the resistance of the wires. The main thing I will be looking for is one reading being significantly different from the other 3, so this should work, even though the long jumper wire will add some extra resistance, but it will be the same for each of the 4 injectors. I plan to back-probe the ECU pins and jumper to the ohmmeter under the hood. I'll report back on results.

 

I misspoke... I plan to remove the ECU A connector and measure resistance at the pins in the cable, not back probe them with the connector in place in the ECU.

 

Starting in 98, Accords had a "chip" in the key for the immobilizer. This is where a replacement ECU/PCM needs to be "re-programmed". Your 5th gen will not need this is you replace the ECU.

As stated, you will need to stick with a 94 or 95 EX (vtec) ECU and be sure it it also the same trans (auto/manual).

 

Thanks for that ECU info about the immobilizer requiring re-programming. That makes me feel better about buying used ECU's for my 94 EX AT. I'll look for the same PN that is in there to make sure it is the correct ECU. Most ads include a photo of the PN label.

 

That worked like a charm and I was finished checking resistance in all 4 injectors in about 15 minutes.... much less time than it would have taken me to remove one of those darned clips and measure one injector and put everything back. I used short pieces of .032 safety wire in the female pins to connect jumper cables to. Three injectors read 3.5 ohms and #3 read 3.4 ohms, so they were consistent, which is what I was looking for.

If you ever need to check injector resistance, this is the way to do it.... it will save you a lot of time and grief when you loose one of those spring clips down in the engine....

 

One other piece of info about the DTC 16 CEL. When I start the car the CEL goes off after a couple seconds as it should and comes back about 15-20 seconds later with the DTC 16 code, so it seems to be sensing something after the car is running and throws the code. I assume if there was a problem with ECU power or grounds, it would throw the code right away, plus it would probably be complaining with other codes. Resistances are good in all injectors and injector resistors, so I don't know what else the ECU senses related to FI. I have run out of things to check, so It is time to buy another ECU, swap ECU's and pray this problem will disappear, but I don't know what else to do.

 

One last update. I received a replacement ECU today that I purchased on eBay, installed it, started up and no more CEL lights!!! YEAH, success!! It was a bad ECU, which was the only thing left to change or check, so the old Accord is back to normal and should pass the emission test like it always has. Big relief to get this fixed. I have recently replaced the ignition switch, the master relay, the fuel injectors, the idle air control valve and installed a new battery today, so hopefully it will be good to go for a good long while. I learned a lot in the process, which is always good.

 

It's funny when the shop manual diagnostic trouble shooting guide gives you all the steps and specifications on how to test these OBD codes. Then when it comes down to the last step as being the possible issue. We seem to second guess ourselves, or the manual, and redo all the testing or start searching for some other thing that could possibly be the issue......lol Guilty of it myself!

Glad to hear that the new ECU cleared the issue.

Should take apart your old ECU and see if there are any burnt out components that could be replaced. Might be worth a few bucks if you can fix it rather than throw it out.

 

Yes, I had read other posts that said only replace the ECU if you are getting code 0, etc, so I certainly had my doubts, but I had checked everything that the manual said to check, including the injector resistances, so after they checked out good, the ECU was all that was left and there are no other test procedures if that doesn't fix it.
All the other stuff I replaced was related to an intermittent no start problem, related to a couple years ago when the car was stolen and the ignition was damaged, so only the injectors and the ECU were involved in getting rid of the 16 code.
I'll open up the old ECU and see what it looks like, but when I opened it before, looking at the back of the board, there were no discolored areas, but I'll open the component side and have a look.
Thanks.

 

90% of the DTC Codes that I have helped to diagnose that end up with a bad ECU have been due to worn out leaking capacitors that burn thru the board trace. The other 10% are caused by burnt out components due to user error, ether a cut wire/short or a wrong component being connected in the engine bay.

 

Tonight I pulled the covers off both sides of the ECU and looked it over carefully with a magnifying glass and found nothing unusual like burnt areas on the board or discolored components. The board looks like new on both sides, but obviously one or more of the IC's or discrete components are having problems. Given that I wasn't able to find and fix a problem, I plan to dispose of the ECU.
Your point about the 10% is well taken and may have happened when a local repair shop worked a couple days on it trying to find the cause of a no start problem, where we had it towed for repair. There are many color coded zip ties on the ECU connector wires and I'm sure there was a good bit of back probing going on around the ECU and think the problem originated there, since it was working fine with no CEL codes before that. After the most recent time where the car stopped and couldn't be started, stranding my step daughter, I noticed the CEL light and pulled the code and found it was 16 pointing to fuel injectors. I assumed the injectors were in need of cleaning and checking, given the high mileage, so I decided to buy new ones, given all the miles on the car. After installing the new injectors, the DTC 16 code was still there, which makes me now believe the injectors were still functioning ok when I removed them and that the ECU problem was already present.
Whatever the cause, I'm very glad to have the problem solved without breaking the bank. I plan to take it on a longer test drive tomorrow, including an emission check, so we'll see what happens.
Thanks to all who replied.

 

It's likely the people somehow did something that fried the ecu, even though it isn't showing any visible signs of issues. Bad ecu's are actually more common than you think. Normally they do show visible signs of issues, a lot of times they are throwing a code 43 which is impossible to fix until the ecu is replaced. This comes up every now and then.