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2003 oldsmobile bravada


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Taylor Electronics
User

Mar 29, 2018, 6:33 PM

Post #1 of 14 (1241 views)
2003 oldsmobile bravada Sign In

Hello Guys my wife have this 2003 oldsmobile bravada and we have been having trouble with the reduced engine power light coming on for last few months we use to pull over to the side and shut the engine off and start it back up and would not see the light for the next mounth or so. but now it have gotten so bad it will come immediately after starting engine. so i purchase a throtte body tb1022d from auto zone with life time after reading the codes and done the relearn procedure but no luck. now i go and purchase a accelerator pedal su12926 with life time from auto zone i went ahead and got both items just incase i half to have it flashe it will be a one time charge.steel it did not relearn so now i takes it to the gm dealer they told me that they were unable to relearn it due to series of codes that needs to be address said it could cost over a $1000.00 i almost had the big one. but it is something at this place is not quite right. god for give me if i am wrong. guys here are the codes p1221 / p1271 / p1635 / p1681 after accelerator replacement p1120 / p1221 / p1271 / p1680 / p1635
i have also check for grounds and clean connectors at fuse box and at pcm do any one have a clue Thanks Guys william


Discretesignals
Ultimate Carjunky / Moderator
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Mar 30, 2018, 8:37 AM

Post #2 of 14 (1148 views)
Re: 2003 oldsmobile bravada Sign In

Do you have a digital volt meter/with back probes and know how to measure and troubleshoot DC electrical circuits?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Taylor Electronics
User

Mar 30, 2018, 12:00 PM

Post #3 of 14 (1131 views)
Re: 2003 oldsmobile bravada Sign In


In Reply To
Do you have a digital volt meter/with back probes and know how to measure and troubleshoot DC electrical circuits?


yes i do have a digital volt meter i works on tvs


Discretesignals
Ultimate Carjunky / Moderator
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Mar 30, 2018, 12:32 PM

Post #4 of 14 (1125 views)
Re: 2003 oldsmobile bravada Sign In

Awesome.

One of the codes in your list that you should start with is the P1635. It deals with the 5 volt reference to the sensors.


Quote
CIRCUIT DESCRIPTION
The powertrain control module (PCM) provides a 5-volt reference to the following sensors:
- The throttle position (TP) sensor 1
- The accelerator pedal position (APP) sensor 2
- The engine cooling fan speed sensor
- The AC pressure sensor
- The fuel tank pressure (FTP) sensor
- The oil pressure sensor (OPS)

The PCM monitors voltage on the 5-volt reference circuit. If the voltage is higher or lower than required, DTC P1635 will set.


You can check the 5 volt reference on any of those circuits with your volt meter or even better an oscilloscope. The 5 volt reference should be close to 5 volts. It shouldn't be dropping out or more or less than 5 volt.

Back probe at one or more of those sensor connectors with your meter or scope referenced to battery negative with the ignition on and with engine running. The two 5 volt ref wires at the throttle body are light blue/black and grey.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Mar 30, 2018, 12:34 PM)


Taylor Electronics
User

Apr 1, 2018, 8:49 PM

Post #5 of 14 (928 views)
Re: 2003 oldsmobile bravada Sign In

 

hello again here are the voltage reading from the throttle body connector with the harness plug in. but please egnore the picture on the right it dose not match my throttle body but the plug is. here is the reading (e) ye 13.1v / (f) br 14.1v / (g) gray 14.2v (h) bl-w 28.4 mv (a) green 4.2v (b) l-blu-bl 5.2v (C) bl 27.9 mv (d) purl 27.9 mv so this is the reading but here is the weird thing i scan the codes again and it say's system pass no fault detected. and i have not cleared the codes. i am scratching my head. Thank william


Discretesignals
Ultimate Carjunky / Moderator
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Apr 2, 2018, 6:34 AM

Post #6 of 14 (873 views)
Re: 2003 oldsmobile bravada Sign In

Thanks for the measurements Smile


hello again here are the voltage reading from the throttle body connector with the harness plug in. but please egnore the picture on the right it dose not match my throttle body but the plug is. here is the reading (e) ye 13.1v / (f) br 14.1v / (g) gray 14.2v (h) bl-w 28.4 mv (a) green 4.2v (b) l-blu-bl 5.2v (C) bl 27.9 mv (d) purl 27.9 mv so this is the reading but here is the weird thing i scan the codes again and it say's system pass no fault detected.


You seems to have a short to battery on the (G) grey wire 5 volt reference for TP sensor 1. It should be a steady 5 volts.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Taylor Electronics
User

Apr 2, 2018, 7:07 PM

Post #7 of 14 (764 views)
Re: 2003 oldsmobile bravada Sign In


In Reply To
Thanks for the measurements Smile


hello again here are the voltage reading from the throttle body connector with the harness plug in. but please egnore the picture on the right it dose not match my throttle body but the plug is. here is the reading (e) ye 13.1v / (f) br 14.1v / (g) gray 14.2v (h) bl-w 28.4 mv (a) green 4.2v (b) l-blu-bl 5.2v (C) bl 27.9 mv (d) purl 27.9 mv so this is the reading but here is the weird thing i scan the codes again and it say's system pass no fault detected.


You seems to have a short to battery on the (G) grey wire 5 volt reference for TP sensor 1. It should be a steady 5 volts.



ok so in outher words this gray wire have came in connect with 12v + and should be 5.0v. i wonder how can this happen like may be a relay. do you have a wiring diagram for this Thank again william



Quote


Taylor Electronics
User

Apr 3, 2018, 4:29 PM

Post #8 of 14 (625 views)
Re: 2003 oldsmobile bravada Sign In

ok if you sent me a diagram i have not received it. and if you have i am not able to retrieve it Thanks again william


Hammer Time
Ultimate Carjunky / Moderator
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Apr 3, 2018, 5:44 PM

Post #9 of 14 (578 views)
Re: 2003 oldsmobile bravada Sign In

Image hosting is not working at the moment so I sent you a diagram by e-mail






~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Apr 3, 2018, 7:49 PM)


Taylor Electronics
User

Apr 4, 2018, 7:02 PM

Post #10 of 14 (464 views)
Re: 2003 oldsmobile bravada Sign In

hello again i got the diagram Thanks. by looking at the yellow wire in the diagram leaves the throttle body and goses to the pcm pin 26. question if i get close as i can to the pcm and cut the yellow wire and if it reads open with it unplug from the throttle body. and turn around and read the outher end of the yellow wire going to the pcm and it reads 12v will this mean i might have a faulty pcm. please correct me if i am wrong. Thanks william


Discretesignals
Ultimate Carjunky / Moderator
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Apr 5, 2018, 5:30 AM

Post #11 of 14 (443 views)
Re: 2003 oldsmobile bravada Sign In

Why would you want to clip the yellow wire? That is the TAC motor circuit. That circuit can have + or - 12 volts on it depending on how the PCM is commanding the TAC motor.

You really want to verify you indeed have 12 volts sitting on the 5 volt ref. Unplug the throttle body connector and measure that pin again to see if it has 12 volts sitting there. If so, inspect the engine harness and look for anything unusual. If all that looks good, measure the 5 volt ref on the other sensors to see if any are measuring the same. If not, then clip the 5 volt ref (grey) near the PCM connector and see if the short goes away. If it doesn't go away, you need really look at the harness thoroughly. If it does go away, you could have a short on another 5 volt ref that shares that same circuit or something happened inside the PCM.

Even thought the 5 volt ref circuit is shown separate in the wiring schematic they are usually shared inside the PCM.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Apr 5, 2018, 7:05 AM)


Taylor Electronics
User

Apr 9, 2018, 8:47 PM

Post #12 of 14 (382 views)
Re: 2003 oldsmobile bravada Sign In

hello again i had my oscilloscope connected to the 5v ref. circuit on the connector going to the throttle body and was watching it as i was moving the harness around on each sensors when i got to the fan clutch saw a bunch of noise on the scope as i was moving the wires around. i replace the fan clutch and now so for so good. i could not have done this if it wasn't for your help i am not a machanic but i am electronically inclined so where can i go on this web site to give a big Thanks williamSly


Hammer Time
Ultimate Carjunky / Moderator
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Apr 10, 2018, 5:08 AM

Post #13 of 14 (373 views)
Re: 2003 oldsmobile bravada Sign In

I would think that your testing would have pointed more to a wiring problem than the fan clutch itself.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
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Apr 10, 2018, 5:55 AM

Post #14 of 14 (367 views)
Re: 2003 oldsmobile bravada Sign In

The fan clutch does use that hall effect sensor inside it to detect fan rpm. It uses the 5 volt ref, so if that sensor is shorting to power or the harness for the fan has wiring problems, that would do it.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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