Hello there everyone. First of all, I hope that things are going well for you all, and second, I was wondering; I read a message somewhere on the group website that talked about completely reseting the computer/module. This entailed something like; turining the ignition on, then pressing the button on the module 5x, then waiting for the light to turn on, then pressing the button again 5x, and waiting for the light to blink. I have been looking hard to find this message, but I can't. Can anyone give me the proper way to reset the module, once all of the problems are fixed, or did I not read something correctly, and I'm blowin' smoke up everyones a#$. :-) If I am, than I'm sorry. You'll have to excuse me, I'm a new Volvo owner, and I don't know any better.

 

You can reset the computer by pulling the fuse for the ECM or disconnecting the battery for 15 minutes.Leave the fuse out for 15 minutes.Which ever way you decide to go.If you disconnect the battery make sure you get the radio code first

 

Mr. Tech, your the BEST!!! Thanks for the info!

 

Your welcome.

 

Where is the fuse for the ECM? I have looked and high low but unsuccessful so far.

Just put new ignition leads and O2 Sensor on, so thought it might like a reset, might fix the idle speed too (idles at about 1000-1100 when warm)

 

It is in the fuse box under the hood.
It should say something like engine computer or ignition or fuel system.

 

Good evening,

In case if removing the fuse or disconnecting the battery for 15 minutes didn't clear the codes (which happened to me a few times, certain codes seem really stubborn), you'd have to clear the codes manually, either via OBD-I terminal or with OBD-II scanner connected at the DLC receptacle in front of the shifter, under the coin holder.

In addition to keeping the codes for radio, make sure that the ECU re-learns idle. When you do this, all electrical loads must be turned off. I usually let the engine idle for 5-10 minutes, but the specified re-learning periodis probably Mr. Tech's jurisdiction (Haynes does not specify).

Best wishes,


JPN

 

I might have missed something but I can't findwhich modelVolvo you are referring too.

Assuming you vehicleis manufactured prior to 2000,then I understand the procedure for resettingfault codes on theearly 850's to that of thelater 850/70's is completely different.

 

Hi, what do you mean by "turning off all electrical loads?" I think I may be having a similar problem with my 850. After replacing O2 sensors, idling is intermittently rough, then the check engine light came on. Replaced the thermostat and coolant temperature sensor (OBD scan said these were faulty), disconnected the battery for 30 min to clear codes, then drove off (I didn't let it idle for a while first). Idling is still rough, and my mechanic is completely stumped!

I will try taking out the fuses for 15 min, then letting it sit and idle for a while. This problem is driving me nuts!

 

Meaning that anything that uses electrical power has to be in "off" position, except the ECUs whose power cannot be cut, or the engine wouldn't run. While you make the ECU re-learn idle, chock the wheels if possible and start the engine with your foot OFF the brake pedal because this causes the rear brake lights to turn on (do not start the engine with the transmission in "N"; must be in "P", for manual gearbox you must chock the wheels). I even disengage the parking brake to turn off the indicator on the instrument cluster. I then let the engine idle for 10 minutes. I am not sure if this is the official procedure, as some seem to note that the car has to be driven for 500 miles, etc...

Some codes cannot be deleted by disconnecting the battery; it would have to be done via OBD-I for '93-'95 models or via OBD-II for some '94 (some '94s did not come with OBD-II)-'97 models.

Let us know if you need additional guidance.


JPN

 

Update: I took out the fuses for 15 min, then put them back in and let the car idle for 10 min with no load. Then, I tunred on the radio, lights, and heater --the car completely freaked out when this happened, extremely rough idle and then it stalled. Restarted the engine and let it idle for 10 min. She calmed down a bit, but is still very rough.

I drove it for a few short trips yesterday, and she's still idling badly intermittently. Shudders, revs up and down, and I can smell gas fumes. Mechanic says drive it around some more in a variety of conditions/speeds, as it may take a while for the computer to adapt. So far I haven't driven it on the highway, or taken it on a long trip.

Has anyone else had this experience? Does the computer usually take a while to learn idling, or does my car just have a learning disability?

Update: Someone's suggested I check the throttle position sensor. Does anyone know of an online guide to doing this? I can't seem to find anything on the forum.

 

When was a tune-up done the last time?

See following as a reference:

https://volvoforums.com/m_48928/tm.htm

Also check for vacuum leak; most likely from plastic elbows.


JPN

 

It has been tuned-up and had its 80,000-mile service in the last month. New O2 sensors, new thermostat and ECT sensor.

Update: I've found bay 13's guide to checking vacuum leaks. I'll give this a shot on the weekend, and I'll also see if cleaning the maf sensor helps. I would like to check the throttle position sensor, but can't find any info on how to do this. Any advice?

Seems like several people have posted similar problems to mine in other threads, so I will let you all know if I find a fix.