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Car Forum / Volvo Cars / March 2006re: 1993 240 DL check engine light issue
Hello: Car was running great but while checking noticed the AMM was failiong on the burnoff test. No check engine light on, but I figured I should be proactive and replace it. Replaced the AMM (Bosch 016) remanufactured unit. ALso replaced air box thermostat with a new OEM unit and cleaned the throttle body intake liberally with CRC. Noticed on the way home that the check engine light was on--and that car was not running as superbly as it had been before. Got home and swapped the old AMM back in figuring the reman unit was defective. Still had check engine light, so cleared the codes on the OBD I port after diagnosing and getting a 1-2-1 code (no signal from AMM or bad AMM (plugged in to port #2, held for 5 seconds, waited, held for 5 more seconds, waited as prescribed in several manuals and then for three seconds.) did this with ignition on but car not running. Did get a 1-1-1 code indicating all was well. Turned off ignition and then started car--only to see check light on again. Cleared code again..but this time at the end instead of 1-1-1 the OBD led's flashed nearly continuously and I heard a clicking sound like a solenoid in that general area. Cleared code once again and at the end instead of 1-1-1 led's flashed almost continuously but with no clicking sound. I'm stumped and car has to pass emission inspection next month--and will not if check engine light is on after vehicle is started. Any tips appreciated. Regards, Doc > Hello: > [quoted text clipped - 39 lines] > > Doc It always cracks me up that the 1 1 1 all clear is the same as the all clear for WWII bombimg raids. There are three access modes to the control unit. Mode 1 (ask the control unit for a response, stored codes, all three registers): Depress button one time. ECU will respond with flash code. Depress once again, and one more time, noting the response codes after each subsequent inquiry. Depress the button two times abount 5 1/2 beats each time to clear the codes. Depress button one time again to verify codes have been erased. Depress button once to exit. Mode 2 (command ECU to ask for switch make/break info): Depress button two times. LED will flash continuously until a switch contact is broken, then the ECU will respond with a flash code verifying communication with the switch. Start with the throttle spool held all the way open. Once the light begins to flash release it just enough to cause the LED to stop flashing. When the light flashes continously again let the throttle return to idle. When the light begins flashing again depress the button one time to exit. The switches are: idle on/off, full throttle, A/C on/off, Transmission N on/off, P on/off. Usually used to verify throttle position switch proper setting. Mode 3 (command ECU to operate components): Depress button three times and the ECU will operate numerous devices. EVAP valve, Injectors, cold start injector, IAC, and repeat for several cycles until it gets tired of playing games. Depress button one time at any point to exit. Verifies wiring integrity to various components. Anytime you want to exit a mode just depress the button one time. If this doesn't work, cycle the key and start over in whatever mode you desire. Bob  SignatureThe goal when driving is to miss the maximum number of objects. <snippet> >> Hello: >> >> Car was running great but while checking noticed the AMM was failiong >> on the burnoff test. Bob wrote <snippet> >It always cracks me up that the 1 1 1 all clear is the same as the all >clear for WWII bombimg raids. [quoted text clipped - 3 lines] >Mode 1 (ask the control unit for a response, stored codes, all three >registers): >Mode 2 (command ECU to ask for switch make/break info): Depress button >two times. LED will flash continuously until a switch contact is broken, > >Mode 3 (command ECU to operate components): Depress button three times >and the ECU will operate numerous devices. EVAP valve, Injectors, cold >Anytime you want to exit a mode just depress the button one time. If >this doesn't work, cycle the key and start over in whatever mode you >desire. > >Bob Hello Bob: I was already aware of the different modes for doing diagnostics on OBD I on the 240, but thanks for posting it as I'm sure it will help others and I've not seen it in most manuals. That said, I tried several times again to clear the code and while it did appear to clear (1-1-1) the check engine light again came on as soon as I started the vehicle--and stayed on. Next thing I tried was removing the NEGATIVE (Earth) battery cable and touching it to the positive terminal for about 15 to 20 seconds with the ignition off. Voila! No more check engine light and OBD diag shows 1-1-1. Then I reinstalled the new AMM...and again a check engine light, so clearly the unit is bad. Swapped the old AMM back in and all was well once I cleared the code using the battery terminal method. Note to anyone who tries this trick: DO NOT disconnect the positive cable. Be sure it's only the Negative (Earth) cable and that ignition is off. Regards, Doc <snip> > Next thing I tried was removing the NEGATIVE (Earth) battery cable and > touching it to the positive terminal for about 15 to 20 seconds with > the ignition off. > > Voila! No more check engine light and OBD diag shows 1-1-1. Not to be picky but it doesn't really matter which cable you remove first. Or whether you remove one or both. The key is touching the two cable ends together which forces any capacitors to discharge and remove the commit charge on any memeory in any system using that method for volatile memory retension. In fact, on airbag cars the Volvo manual requests that whenever you are removing the air bag or working on the system you should always disconnect the the + cable. Furthermore they request that you turn the key to the run position before reconnecting the cable. The logic being that if there were to be a fault that had not been addressed during repairs then you would be safely outside the passenger compartment should the bag detonate unintentionally. Bob SignatureThe goal when driving is to miss the maximum number of objects. > Not to be picky but it doesn't really matter which cable you remove > first. Or whether you remove one or both. The key is touching the two [quoted text clipped - 9 lines] > > Bob I've developed the habit of removing the negative cable because the wrench used on the bolt is not "hot" that way. Once the negative terminal is removed the positive can be removed without fear of creating the shower of sparks. For people less klutzy than I it may not be important. Mike >> Not to be picky but it doesn't really matter which cable you remove >> first. Or whether you remove one or both. The key is touching the two [quoted text clipped - 18 lines] > > Mike That is excatly why also Volvo has the following text in their generally safety information in workshop manuals, "To help prevent sparking when removing a battery, always disconnect the negative battery lead first. Connect the positive lead first when installing a battery" Regards Per Hauge > >> Not to be picky but it doesn't really matter which cable you remove > >> first. Or whether you remove one or both. The key is touching the two [quoted text clipped - 28 lines] > > Per Hauge Agreed, but in this one situation they are quite adamant about removing and replacing only the positive cable. Bob SignatureThe goal when driving is to miss the maximum number of objects. > Agreed, but in this one situation they are quite adamant about removing > and replacing only the positive cable. > > Bob Any idea why that is? Mike >> >> Not to be picky but it doesn't really matter which cable you remove >> >> first. Or whether you remove one or both. The key is touching the two [quoted text clipped - 38 lines] > > Bob Would this be relevant for all models any year or is it specific? Regards Per Hauge > >> >> Not to be picky but it doesn't really matter which cable you remove > >> >> first. Or whether you remove one or both. The key is touching the two [quoted text clipped - 33 lines] > >> > >> Per Hauge It was in the airbag paper manuals in the mid nineties. Applied to all models. Bob SignatureThe goal when driving is to miss the maximum number of objects. > I'm stumped and car has to pass emission inspection next month--and > will not if check engine light is on after vehicle is started. > > Any tips appreciated. If it ain't broke, don't fix it. SORRY couldn't resist. |
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