ECM not going into close loop
#1
01-15-2008, 11:21 AM
ECM not going into close loop
I have a problem that I posted on two different S10 sites and got no responses so I'd like to try it here because you guys rock!
I bought an 89 S10 short bed 4x4 with a 4.3 tbi. The truck has sat for over 6 mo. but starts right up since I did a tune up. Though the check engine lite is not on I ran a scan with my autoxray 6000. It first should a code 15 which prompt me to repair the corroded connector to the ECT sensor.
The problem I have is the ecm does not go into close loop even after the ECT reads 197 deg. I've only driven it once down my road for a short run because the registration is expired. I ran the engine in park for over 15 minutes and it still stays in open loop. My scanner shows that the temp is normal. The 02 is fluctuating so it's not dead but I know the ecm is ignoring it because it's still in open loop. Also the scanner read something about a learn mode disabled and I don't know what that means. Do you actually have to drive it for for several miles for the ecm to go into close loop? I thought that as long as it sees the ECT at normal operating temp, should go in to close loop? Any replies are appreciated.
One more question, there is a little electric box or module of some sort bolted piggyback to the ecm. I couln't find it in my Haynes. Can anyone tell me what this is? It's about the size of a pocket wallet.
I bought an 89 S10 short bed 4x4 with a 4.3 tbi. The truck has sat for over 6 mo. but starts right up since I did a tune up. Though the check engine lite is not on I ran a scan with my autoxray 6000. It first should a code 15 which prompt me to repair the corroded connector to the ECT sensor.
The problem I have is the ecm does not go into close loop even after the ECT reads 197 deg. I've only driven it once down my road for a short run because the registration is expired. I ran the engine in park for over 15 minutes and it still stays in open loop. My scanner shows that the temp is normal. The 02 is fluctuating so it's not dead but I know the ecm is ignoring it because it's still in open loop. Also the scanner read something about a learn mode disabled and I don't know what that means. Do you actually have to drive it for for several miles for the ecm to go into close loop? I thought that as long as it sees the ECT at normal operating temp, should go in to close loop? Any replies are appreciated.
One more question, there is a little electric box or module of some sort bolted piggyback to the ecm. I couln't find it in my Haynes. Can anyone tell me what this is? It's about the size of a pocket wallet.
#2
01-17-2008, 09:40 AM
RE: ECM not going into close loop
Do you know if anything has been done to the truck? If you can't find the "black box" in the Hayne's manual, it may not be stock. Have you tried taking it off and running the truck? If the "black box" is some sort of chip or programmable unit, it may be telling the computer to stay in open loop for some reason.
#3
01-19-2008, 11:41 PM
RE: ECM not going into close loop
One of my forums responded and said the little module is for the DRAC but he never explained what a DRAC is so I'm still waiting a reply.
As far as I know the ecm looks unaltered and the service # did match the vehicle year/model. I bought the S10 truck to swap its entire eng/drive train into an older S10 to replace the puny 2.8. I still can't figure out why I've got no codes, runs quite well, reaches operating temp,but still won't close loop. I'm guessing maybe I need to put actual driving time on it but that's now impossible because I've pulled the rusted body off. thanks
As far as I know the ecm looks unaltered and the service # did match the vehicle year/model. I bought the S10 truck to swap its entire eng/drive train into an older S10 to replace the puny 2.8. I still can't figure out why I've got no codes, runs quite well, reaches operating temp,but still won't close loop. I'm guessing maybe I need to put actual driving time on it but that's now impossible because I've pulled the rusted body off. thanks
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