P0141 still being set
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From: johngdole on 8 Sep 2007 23:14 Yes, Dave. That's precisely what I had been saying. The excellent Bosch sensors are fine. I was trying to help you avoid swapping parts trying to make it work. And I was pointing to the ECU fault all this time. Why? In order for the heater to turn on, the ECU has to activate a grounding transistor. Call it a switch if you will. If this switch isn't turned on, the heater WILL BE OFF. Now there are some conditions under which the heater will be turned on, so it's best to test this within minutes of a cold engine start. All you have to measure is the heater ground that goes through the ECU, and see if it actually goes to ground. If it doesn't under the condition requiring the heater, then the ECU most likely BAD. And you should substitute a known good ECU for AN ADDITIONAL VERIFICATION TEST. In addition, there are circuits around this transistor that may be bad and resulting in the P0141 code. Nothing in Ray O's comments even suggest testing this part. I'm disappointed that the self proclaimed Toyota tech even suggested that the ECU is not likely the problem without performing this important test. I don't think he knows how the ECU controls the oxygen sensor. On Sep 8, 4:37 pm, "davejohan...(a)gmail.com" <davejohan...(a)gmail.com> wrote: > 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? > > 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
From: johngdole on 8 Sep 2007 23:20 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.". On Sep 5, 9:52 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: > <johngd...(a)hotmail.com> wrote in message > > news:1189048835.035611.70850(a)w3g2000hsg.googlegroups.com... > > > Dave is looking at a new sensor. And I'm telling him to hold the > > horses and diagnose the grounding path through the ECU. It's > > irresponsible for anyone to suggest purchasing new parts when the > > diagnosis isn't even complete. Besides, the splice was put in for the > > old sensor, presumably the OEM Denso. > > We agree, although I'm not speculationng on why the splice was put in. > > > > > The mechanic who put in the splice obviously knew about the problem in > > the ECU's ground path. That's why he bypassed it. The splice is a no- > > no, but at least the mechanic knew what connects to what. Perhaps Ray > > can enlighten us some more on the transistor switch in the ECU for the > > heater. He should know. > > As far as I know, none of the wires between the O2 sensor and the ECU should > be grounded, and grounding those wires may have damaged the ECU. > > > > > As far as compatibility goes: people don't use Toyota gas, fill their > > non-Toyota tires with Toyota air or drive on Toyota roads. Ray said no > > Denso problems? Perhaps he never fixed any of the Toyota TSB > > #EG014-03? > > > EG014-03 M.I.L. ON DTC P1130, P1135, P1150 OR P1155 - Under certain > > driving conditions, some 2002 model year Camry vehicels with V6 > > engines may exhibit a M.I.L. "ON" with one of the following DTCs as a > > result of an Air Fuel (A/F) Sensor manufacturing and installation > > issue > > That TSB refers to conditions with Camrys, while the OP has a Prism, but I > get your point ;-) What I should have said is that I have never run into > compatibility problems with Denso, while I have occasionally run into > compatibility problems with Bosch. As I said before, Bosch is a good brand > and I have seen them work perfectly fine in many cases, but when trying to > fix a "problem" car, putting in Denso parts has worked in many cases. I can > think of no logical reason why this is the case since the specs on the Bosch > replacement parts are at least equal to the Denso parts. > > -- > > Ray O > (correct punctuation to reply)
From: mrsteveo on 9 Sep 2007 00:59 On Sep 8, 8:20 pm, johngd...(a)hotmail.com wrote: > 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.". > > On Sep 5, 9:52 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: > > > <johngd...(a)hotmail.com> wrote in message > > >news:1189048835.035611.70850(a)w3g2000hsg.googlegroups.com... > > > > Dave is looking at a new sensor. And I'm telling him to hold the > > > horses and diagnose the grounding path through the ECU. It's > > > irresponsible for anyone to suggest purchasing new parts when the > > > diagnosis isn't even complete. Besides, the splice was put in for the > > > old sensor, presumably the OEM Denso. > > > We agree, although I'm not speculationng on why the splice was put in. > > > > The mechanic who put in the splice obviously knew about the problem in > > > the ECU's ground path. That's why he bypassed it. The splice is a no- > > > no, but at least the mechanic knew what connects to what. Perhaps Ray > > > can enlighten us some more on the transistor switch in the ECU for the > > > heater. He should know. > > > As far as I know, none of the wires between the O2 sensor and the ECU should > > be grounded, and grounding those wires may have damaged the ECU. > > > > As far as compatibility goes: people don't use Toyota gas, fill their > > > non-Toyota tires with Toyota air or drive on Toyota roads. Ray said no > > > Denso problems? Perhaps he never fixed any of the Toyota TSB > > > #EG014-03? > > > > EG014-03 M.I.L. ON DTC P1130, P1135, P1150 OR P1155 - Under certain > > > driving conditions, some 2002 model year Camry vehicels with V6 > > > engines may exhibit a M.I.L. "ON" with one of the following DTCs as a > > > result of an Air Fuel (A/F) Sensor manufacturing and installation > > > issue > > > That TSB refers to conditions with Camrys, while the OP has a Prism, but I > > get your point ;-) What I should have said is that I have never run into > > compatibility problems with Denso, while I have occasionally run into > > compatibility problems with Bosch. As I said before, Bosch is a good brand > > and I have seen them work perfectly fine in many cases, but when trying to > > fix a "problem" car, putting in Denso parts has worked in many cases. I can > > think of no logical reason why this is the case since the specs on the Bosch > > replacement parts are at least equal to the Denso parts. > > > -- > > > Ray O > > (correct punctuation to reply) ..... or RayO has done enough repairs and seen enough diagnostics to know what is a likely culprit and what isn't. I would imagine Bosch is a fine brand however Bosch is not Toyota OEM and most of us have all seen instances where non-OEM parts cause strange issues. Most tend to troubleshoot from the easiest to the most difficult.
From: davejohansen on 9 Sep 2007 03:42 On Sep 8, 8:14 pm, johngd...(a)hotmail.com wrote: > Yes, Dave. That's precisely what I had been saying. The excellent > Bosch sensors are fine. I was trying to help you avoid swapping parts > trying to make it work. > > And I was pointing to the ECU fault all this time. > > Why? In order for the heater to turn on, the ECU has to activate a > grounding transistor. Call it a switch if you will. If this switch > isn't turned on, the heater WILL BE OFF. Now there are some conditions > under which the heater will be turned on, so it's best to test this > within minutes of a cold engine start. > > All you have to measure is the heater ground that goes through the > ECU, and see if it actually goes to ground. If it doesn't under the > condition requiring the heater, then the ECU most likely BAD. And you > should substitute a known good ECU for AN ADDITIONAL VERIFICATION > TEST. In addition, there are circuits around this transistor that may > be bad and resulting in the P0141 code. > > Nothing in Ray O's comments even suggest testing this part. I'm > disappointed that the self proclaimed Toyota tech even suggested that > the ECU is not likely the problem without performing this important > test. I don't think he knows how the ECU controls the oxygen sensor. > > On Sep 8, 4:37 pm, "davejohan...(a)gmail.com" <davejohan...(a)gmail.com> > wrote: > > > 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? > > > 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 Thanks for the info and I'm VERY grateful for your advice, but I think that you're being a little harsh towards Ray O. I'm just glad that I have people like you, him, and everyone else here who is willing to lend a hand and give whatever advice they have. Also, I have heard from several other people that it's VERY uncommon for ECUs to go bad, so I agree with mrsteveo that Ray O was just following the natural path of investigating/fixing the easiest/most likely problem first. But to the main point, I don't exactly have access to a "working" ECU to verify against. I could go and try and find one at a junk yard and hope that the one I get is good, but do you think it would be easier for me to just take it to the dealer and have them fix it now? If that is the best option, then what do you think I should expect to pay for something like that? And thanks again for all of the help, Dave
From: Ray O on 9 Sep 2007 22:28
<davejohansen(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. 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) |