Ok355

I have a 1999 Civic GX (compressed natural gas powered engine), 30k. Automatic trans. All Stock. New battery.

-CEL is on.
-The engine idles / revs high & low constantly. When I drive it stays at a higher than normal rev, but at idle it is erratic.
-The speedometer and mileage counter do not move when driving. The rest of the instrument cluster works, including the fuel and temp gauges.

I have encountered these codes:

P1298 Injector Driver Module Failure
P0135 H025 Heater Circuit, Bank 1 Sensor 1
P0141 H025 Heater Circuit, Bank 1 Sensor 2

I saw in a FAQ that the P1298 was listed as something else, Electric Load Detector (ELD) Circuit High Voltage. However, I am confident that mine is related to the Injector Driver Module Failure, but I am not sure how to rule out CHV.

1. Do these codes work together, one triggering the next?
2. Have you ever encountered these codes all at the same time?
3. In light of the P1298 fault, my greatest concern is the cost of replacing the Injector Driver Module, any idea how much this part costs? Is there any way to test the questionable part?

Any help would be great. Thanks.

grumblemarc

iTrader: (4)

P1298 is Electric Load Detector (ELD) Circuit High Voltage
Here's a search for this CEL for all of H-T. I don't see any of them saying this CEL has anything to do with any Injector Driver Module. That's why it's also in the FAQ.
http://www.google.com/search?q=site%...ient=firefox-a

How are you pulling these codes?

lazlong

From what I've seen, a lot of the time replacing the ELD will make all the codes disappear.

Former User

Click the Fuse 15 TSB in my signature.

Ok355

@ RonJ@HT:
Fuse #15 (7.5amp) was blown. I looked at the engine wiring harness near the intake manifold bracket and could not find any damaged wires, however considering the tight location I do intend to look at this again much more thoroughly after finding that fuse #15 was blown. I can't see how else fuse #15 would blow unless a wire is damaged on the harness. What do you think Ron?

@ grumblemarc & lazlong:
The codes were pulled via a ScanGauge. I pulled an ELD out of my 99 Civic Si and put it in my 99 Civic GX. The part fit and plugged-in, however I am not sure if they are setup for different voltage parameters. Any idea if the ELD's are all the same?

Presently it is still idling high and then low. When you start the engine it idles normal for about 2 mins, then the check engine light comes on and the fluctuating idle begins... It appears to be revving an additional 1000rpms over the normal idle range and then dropping to approx 500rpm's. As would be expected the latter is causing the automatic transmission to shift strange as well.

On Saturday I am going to try to pull the ELD & the 02 Sensors out of another low mileage 99 Civic GX. I will post an update after the swap.

Is there anything else to look out for?

Former User

Spend more time inspecting the wire harness. It's a very common problem.

Ok355

Ron,

Here is the latest. Today I checked fuse #15 again and it was blown for a second time. I closely and thoroughly checked the wires by the intake manifold bracket, they all look good. However, I am certain I have found what is blowing fuse #15... I found 4 burned wires which connect to the downstream oxygen sensor. I unplugged the downstream oxygen sensor, replaced fuse #15 for a 3rd time and started the engine, then checked the fuse, it was still good. The engine was idling correctly so I drove it around the block for 5 minutes with no problems, after 7 minutes the engine idle started to rise and fall again. This time around, I suspect the latter is due to me disconnecting the downstream oxygen sensor (please correct me if that assumption sounds wrong). I returned to my house, turned the engine off and decided to plug the downstream oxygen sensor connector back into the engine wiring harness. As soon as I turned the key to position two, fuse #15 blew again. ....I did this to triple check that this was the cause for the fuse failure.

One thing I am certain about is that the 4 exposed wires were burned, as I found them laying across the exhaust heat shield. I intend to remove the oxygen sensor, cut the 4 wires, re-solder and seal them, then I will plug the sensor back in and see what happens to fuse #15.

As you know, there are two oxygen sensors, if the lower one of the two is not working and/or disconnected will it cause the engine to idle erratically?

Thanks

lazlong

Yes, that's how the computer reads how well the cat and primary sensor are doing. If it doesn't know how well the cat and sensor are doing their jobs it can't adjust the fuel trim right, hence the weird idle.

Former User

Nice job. You definitely found the problem.

No. The secondary O2 sensor plays an emissions role in monitoring whether the catalytic converter is working. It has no other function.

Ok355

New Problem. My OBDII is not working.

I've spent 3 weeks going over everything I was advised to look for, but just couldn't solve the bad idle. I decided to take my Civic to my trusted mechanic whom my family has come to trust over the past 20 years. He tried to run his expensive scan tool on my Civic and could not get any reading at all, as if the scan tool was not working. So next I drove the car to O'reilly's (an auto parts store) to have them scan it for codes. They could not get their scan tool to work either. Called my Honda dealer and they said they can't help me if they can't pull up any trouble codes.

Even though the idle would rise and fall 1000 rpm's while in park, I could still drive it and being in gear kept the idle steady. However, I decided to drive my Civic from the mechanic to my house and on the way, the idle went from odd to a lot worse. Now the idle hunts very erratically while in park, and when driving it nearly stalls out and stumbles.

In my earlier and original post a scan tool was working and getting codes. Now a month later scan tools can not pull any codes from the OBDII system.

What could be causing the OBDII not to work?

HondaPartsHero

http://www.clubcivic.com/board/showthread.php?t=180624

from another board from RonJ

Ok355

Thanks HondaPartsHero.

You nailed it with the post you sent me. My ceiling & trunk lights are out, about a week ago I pulled a 7.5 amp fuse from slot 43 to use in slot 15. My bad!

Thank you for saving me from having to buy a new ecu. Forums and people like you save others from big expenses.

Ok355

Problem solved.

After I replaced the bad 02 sensor that cleared the codes at the heading of this post P1298, P0135, P0141. The engine was still idling terribly, even worse than before, so I ran another scan and found these 2 codes: P0505 Idle Air Control System Fault & P1509 Idle Air Control Valve Circuit Failure.

I decided to replace the IACV with an OEM one for $155 and sure enough it fixed the problem instantly! No codes, no CEL. The engine runs great and idles just as it should.

1999 Civic GX (compressed natural gas powered engine).

Thanks to everyone who helped me.