P0141 still being set
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From: Ray O on 9 Sep 2007 23:36 <johngdole(a)hotmail.com> wrote in message news:1189308027.483409.13040(a)w3g2000hsg.googlegroups.com... > Ray, I was asking to see if you know how the ECU controls the oxygen > sensor heater and check it's proper operation. It was an opportunity > to demonstrate your knowledge from taking Toyota courses, if any. > > I don't think you know anything about it. Otherwise you would have > asked Dave to check the grounding circuitry in the ECU that turns on > the oxygen sensor heater. Instead of dweeling on the sensor and > telling him "OK, next time you buy an O2 sensor, get a Denso.". > John, We have come to the same conclusion, but through a different path. You seem to be offended by the advice I am giving, and that is absolutely not my intent. Even though I am not an expert in electronics, I have had good results by making sure technicians have followed all of the steps in the factory repair manual (unfortunately, steps get skipped fairly often by experienced technicians because their experience lets them get away with it most of the time). I don't think that the blue-black wire that the Dave described as cut and grounded in one of his earlier posts is supposed to be grounded. In a later post, he said that proper voltage between the terminal at the end of the blue-black wire and ground is 12 volts. I don't know what grounding that wire would do the ECU - would that damage the ECU? The reason that I did not tell Dave to check the grounding circuitry in the ECU that turns on the O2 sensor heater is that I think the grounding is inside the ECU and not testable without opening up the ECU. In a simple circuit, Toyota generally does not run ground wires all the way from a component to the ECU if the component can be grounded with a shorter wire. My assumption is that the heater return wire has to have voltage when it gets back to the ECU, and if the wire is grounded before the ECU, the ECU won't see the correct voltage and assume an open or short circuit. I am not right 100% of the time. I only looked at cars that the dealers had problems with and can only recall 3 occasions where I had to have an engineer look at something I couldn't fix. Two of those vehicles were diesels, which I have no experience on, and we bought back the third one because we couldn't find the problem. An employee bought that third one and never experienced the problem that the original customer had. Perhaps this is another occasion where I am wrong, but in my opinion, one can't go wrong by starting with the basics. -- Ray O (correct punctuation to reply)
From: davejohansen on 10 Sep 2007 00:33 On Sep 9, 7:28 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: > <davejohan...(a)gmail.com> wrote in message > > news:1189294670.083939.255150(a)d55g2000hsg.googlegroups.com... > > > > > On Sep 4, 7:55 pm, johngd...(a)hotmail.com wrote: > >> This may indicate that the previous mechanic tried to fix a grounding > >> problem for the Heater Return (for the lack of a better term) wire > >> from the sensor. Which means the transistor in the ECU may be bad and > >> not dropping the heater return line to ground when the ignition is > >> turned ON. So the previous mechanic splices the return wire directly > >> to ground, hoping to solve the problem which he obviously didn't do. > >> That's why you see a splice from the return directly to ground -- it's > >> a futile attempt to bypass that grounding transistor "switch" that > >> turns on the heater in the ECU. > > >> So do this check: > > >> Since you already checked and had battery voltage at the Heater Battery > >> + wire, you need to check the Heater Return wire and make sure it goes > >> to ground and therefore completes the circuit that turns on the > >> heater. > > >> So at the oxygen sensor's connector towards the ECU, and with the > >> ignition switch to ON, check the continuity of the Heater Return wire > >> to Ground. Do you see continuity to Ground? (Be careful not to > >> connect the ohmmeter to battery voltage wire or you'll fry the > >> meter). > > > I got the Denso O2 Sensor and it still popped up the code, so I > > decided to rip everything apart and redo the wiring check. Here's the > > steps I followed > > > 1) Disconnect the O2 Sensor. Turn ignition on. Check the voltage > > between ground and the O2 Sensor Terminal 1 (Black/Red wire) and > > ensure that it's 12 V. > > RESULT: It read 12.4 V. > > 2) Turn ignition off. Reconnect the O2 Sensor. Disconnect ECU > > Connectors. Turn ignition on. Check the voltage between ground and > > terminal 19 (Blue/Black wire) of the 26-pin ECU connector and ensure > > that the voltage is at least 10 V. > > RESULT: It read 12.4 V. > > 3) Turn ignition off. Disconnect the O2 Sensor. Check the resistance > > between O2 Sensor Terminal 1 (connects to the Black/Red wire) and O2 > > Sensor Terminal 2 (Connects to the Blue/Black wire) and ensure that > > it's between 11.7 and 14.3 Ohms at 68 degrees F. > > RESULT: The Bosch one is 9 Ohms and the Denso one is 16 Ohms, but I > > think those are both close enough and that's not the problem. > > > The diagnostics say that if all of these tests pass, then you should > > change the ECU, but from the comments on here it sounds like that's > > not likely. > > > I also did the test that John Dole suggested to check for continuity > > between the pin on the ECU and ground and it didn't pass. I'm not an > > electrician, so here's what I did and someone can tell me if it was a > > correct check. I hooked an alligator clip with a long cable to the > > ground terminal of the battery and connected one probe of the multi- > > meter to it. I then probed Terminal 19 on the ECU with the other probe > > and it didn't show a connection (didn't beep and didn't show any > > resistance). Is that the right way to check for continuity between > > ground and the ECU? > > I don't have a wiring diagram or manual handy, but in Step 2 above, you said > that the voltage between terminal 19 and ground is 12.4 volts, which means > that terminal 19 is not a ground pin. If terminal 19 was a ground pin, then > the voltage between terminal 19 and ground should be 0. Sorry, I wasn't clear about what I was probing. In Step 2, I was actually probing the pin on the ECU connector that connected to Terminal 19 on the ECU (and not the Terminal 19 pin). In summary, the voltage on Terminal 19 of the connector was 12 V and there was no voltage (no connection) on Terminal 19 itself. Sorry about the ambiguity, but I'll look into testing against another ECU. Dave > > Since terminal 19 is not a ground pin, then there should not be any > continuity between ground or the battery negative terminal and terminal 19. > > The process you used to check for continuity between ground and the ECU is > correct, except that you have to find out which ECU terminal is the ground > terminal. > > > But with all of that info, does anyone have any ideas on what's wrong? > > I think that the O2 Sensor itself is fine and it looks like the wiring > > between the O2 Sensor and the ECU is fine, so is it the ECU itself > > that's bad? Or is there some other wiring that's wrong? And how do I > > find out what wiring is bad? > > > Thanks again for all of the help, > > Dave > > While bad ECU's are extremely rare, they do occasionally go bad or are > damaged. At this point, an ECU replacement is probably in order. The best > thing to do would be to borrow a known good ECU and swap to see what > happens. > -- > > Ray O > (correct punctuation to reply)
From: Ray O on 10 Sep 2007 01:31 <davejohansen(a)gmail.com> wrote in message news:1189398793.630942.29310(a)r29g2000hsg.googlegroups.com... > On Sep 9, 7:28 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: >> <davejohan...(a)gmail.com> wrote in message >> >> news:1189294670.083939.255150(a)d55g2000hsg.googlegroups.com... >> >> >> >> > On Sep 4, 7:55 pm, johngd...(a)hotmail.com wrote: >> >> This may indicate that the previous mechanic tried to fix a grounding >> >> problem for the Heater Return (for the lack of a better term) wire >> >> from the sensor. Which means the transistor in the ECU may be bad and >> >> not dropping the heater return line to ground when the ignition is >> >> turned ON. So the previous mechanic splices the return wire directly >> >> to ground, hoping to solve the problem which he obviously didn't do. >> >> That's why you see a splice from the return directly to ground -- it's >> >> a futile attempt to bypass that grounding transistor "switch" that >> >> turns on the heater in the ECU. >> >> >> So do this check: >> >> >> Since you already checked and had battery voltage at the Heater >> >> Battery >> >> + wire, you need to check the Heater Return wire and make sure it goes >> >> to ground and therefore completes the circuit that turns on the >> >> heater. >> >> >> So at the oxygen sensor's connector towards the ECU, and with the >> >> ignition switch to ON, check the continuity of the Heater Return wire >> >> to Ground. Do you see continuity to Ground? (Be careful not to >> >> connect the ohmmeter to battery voltage wire or you'll fry the >> >> meter). >> >> > I got the Denso O2 Sensor and it still popped up the code, so I >> > decided to rip everything apart and redo the wiring check. Here's the >> > steps I followed >> >> > 1) Disconnect the O2 Sensor. Turn ignition on. Check the voltage >> > between ground and the O2 Sensor Terminal 1 (Black/Red wire) and >> > ensure that it's 12 V. >> > RESULT: It read 12.4 V. >> > 2) Turn ignition off. Reconnect the O2 Sensor. Disconnect ECU >> > Connectors. Turn ignition on. Check the voltage between ground and >> > terminal 19 (Blue/Black wire) of the 26-pin ECU connector and ensure >> > that the voltage is at least 10 V. >> > RESULT: It read 12.4 V. >> > 3) Turn ignition off. Disconnect the O2 Sensor. Check the resistance >> > between O2 Sensor Terminal 1 (connects to the Black/Red wire) and O2 >> > Sensor Terminal 2 (Connects to the Blue/Black wire) and ensure that >> > it's between 11.7 and 14.3 Ohms at 68 degrees F. >> > RESULT: The Bosch one is 9 Ohms and the Denso one is 16 Ohms, but I >> > think those are both close enough and that's not the problem. >> >> > The diagnostics say that if all of these tests pass, then you should >> > change the ECU, but from the comments on here it sounds like that's >> > not likely. >> >> > I also did the test that John Dole suggested to check for continuity >> > between the pin on the ECU and ground and it didn't pass. I'm not an >> > electrician, so here's what I did and someone can tell me if it was a >> > correct check. I hooked an alligator clip with a long cable to the >> > ground terminal of the battery and connected one probe of the multi- >> > meter to it. I then probed Terminal 19 on the ECU with the other probe >> > and it didn't show a connection (didn't beep and didn't show any >> > resistance). Is that the right way to check for continuity between >> > ground and the ECU? >> >> I don't have a wiring diagram or manual handy, but in Step 2 above, you >> said >> that the voltage between terminal 19 and ground is 12.4 volts, which >> means >> that terminal 19 is not a ground pin. If terminal 19 was a ground pin, >> then >> the voltage between terminal 19 and ground should be 0. > > Sorry, I wasn't clear about what I was probing. In Step 2, I was > actually probing the pin on the ECU connector that connected to > Terminal 19 on the ECU (and not the Terminal 19 pin). In summary, the > voltage on Terminal 19 of the connector was 12 V and there was no > voltage (no connection) on Terminal 19 itself. > > Sorry about the ambiguity, but I'll look into testing against another > ECU. > Dave > If you are disconnecting the harness from the ECU and checking the pin that connects to terminal 19 of the ECU and getting 12 V, and the wire connected to that connector is the blud and black one, then it should not be connected to ground. Good luck! -- Ray O (correct punctuation to reply)
From: Ray O on 11 Sep 2007 22:59 <davejohansen(a)gmail.com> wrote in message news:1189536852.227297.292140(a)z24g2000prh.googlegroups.com... <snipped> >> Maybe email your VIN # and other pertinent details to the local Geo/ >> Chevy dealer? I would imagine they could reference a part # and/or >> cross reference... > > I was able to get the part number from the Chevy dealer by giving them > the last 8 digits of my VIN, so that worked out great. > > Also, the owner of one of the eBay sites recommended that I check out > this website: > http://car-part.com/ > I was able to find an ECU for $59 plus shipping there, so I would > recommend checking out that site in the future for anyone looking for > a tough to find replacement part. > Thanks again for all the help and I'll let everyone know if this > finally fixes my problem, > Dave > Make sure the wire harness doesn't have any extraneous grounding wires or cuts in the insulation before you install the replacement ECU. good luck! -- Ray O (correct punctuation to reply)
From: mrsteveo on 12 Sep 2007 00:18
On Sep 11, 7:59 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: > <davejohan...(a)gmail.com> wrote in message > > news:1189536852.227297.292140(a)z24g2000prh.googlegroups.com... > <snipped> > > > > >> Maybe email your VIN # and other pertinent details to the local Geo/ > >> Chevy dealer? I would imagine they could reference a part # and/or > >> cross reference... > > > I was able to get the part number from the Chevy dealer by giving them > > the last 8 digits of my VIN, so that worked out great. > > > Also, the owner of one of the eBay sites recommended that I check out > > this website: > >http://car-part.com/ > > I was able to find an ECU for $59 plus shipping there, so I would > > recommend checking out that site in the future for anyone looking for > > a tough to find replacement part. > > Thanks again for all the help and I'll let everyone know if this > > finally fixes my problem, > > Dave > > Make sure the wire harness doesn't have any extraneous grounding wires or > cuts in the insulation before you install the replacement ECU. > > good luck! > > -- > > Ray O > (correct punctuation to reply) Speaking of, I found an ECU out of boredom on eBay that appears to match specs / part #'s with my current one. They only wanted $5.00 + $20 shipping. I figured I would buy it since it was cheap. Doubt I would ever need it. Anyway, they claim it should be fine and such. Seems a little odd it was so cheap. So, since I have never seen one... are they easy to hook up to an electrical source? I'd love to hook one up and get some software and the stuff for my laptop and actually play with one... that I can't harm. Or if that's too much hassle -- perhaps just save it in case I ever happen to need it. |