'05 V8 Throttle Position Sensor Codes - Won't Start?

H

Hog_runner

New member
A couple of weeks ago I was in a bind and had a shop replace my starter. They snapped the wires at the connector for one of my knock sensors so I went under and repaired that myself. So after that job I thought damn, I need to clean this engine bay up. Well, I did, and now I can't get to start. Been digging on the forums all day and can't find anything so I'd appreciate y'alls input.

Symptoms:
  • The truck turns over but gives up after the 3-4 second "auto" start.
  • P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
  • P0123 Throttle/Pedal Position Sensor/Switch A Circuit High
  • P2135 Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
My hunch is that I fried the throttle position sensor while cleaning my engine bay. According to DTC codes and referencing FSM (2006 ed.), looks like my options are replace the Throttle Body (to replace the throttle position sensor which is integrated to the TB), or replace the ECM if in actuality that is my problem. I think the ECM is fine though based on my ability to get readings thru my OBD scanner? I guess I'm confused why the car won't start even if the TB/Position Sensor is shorted/open/otherwise fried. I've been racking my brain all day. The FSM mentions a fail-safe mode if the throttle pos. sensor is out that would allow the truck to run in "limp mode" as I've seen it referenced here before. I guess maybe the intake could be out of sync and therefore not getting the correct air/fuel mixture?

Additional info/things I've tried:
  • charged battery
  • opened fuel cap, reinstalled
  • disconnected battery overnight
  • confirmed throttle body opens when accelorator is depressed
  • MAF picks up signal when air blown manually
  • ECM registers throttle opening position (thru OBD scanner)
  • I have gas :)
  • No blown fuses
I have not checked fuel delivery since I'm getting codes related to intake/throttle.
 
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Update: still troubleshooting. I've replaced the throttle body (for new throttle position sensor) as well as MAF, still same symptoms. Turns over just won't start. It has been 1 week and though it is winter we have had a few days hit highs of mid 50's and sunny. So I think there would have been ample time to dry out any connectors that may have gotten soaked. I now think I have fried my ECU. I have a new ECU on order thru ebay but I want to try to track down where the short was created before installing the new ECU and potentially frying it all over again.

FYI for future reference: just stay away from water hose in the engine bay. I know some of you are rolling your eyes, I get it. I was just trying to take care of my stuff so don't bust my balls. I did some searching here about others using pressure washers with no issue, so I thought I'd be safe. I did a procedure similar to ChrisFix on youtube. I have done that procedure twice between my old 2012 FJ Cruiser and my wife's car. During my research here, I've learned about how sensitive these 4th gens are to water. Too many threads from creek crossers frying ECU's.

I'll keep this thread updated as I go. But I sure would take any input from anyone who has had or heard of similar situations.
 
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Did you ever figure this out? I've been fighting 0121 and 0123 codes for like three years now.. Dealership hasn't even been able to figure it out.
 
Hog_runner said:
Update: still troubleshooting. I've replaced the throttle body (for new throttle position sensor) as well as MAF, still same symptoms. Turns over just won't start. It has been 1 week and though it is winter we have had a few days hit highs of mid 50's and sunny. So I think there would have been ample time to dry out any connectors that may have gotten soaked. I now think I have fried my ECU. I have a new ECU on order thru ebay but I want to try to track down where the short was created before installing the new ECU and potentially frying it all over again.

FYI for future reference: just stay away from water hose in the engine bay. I know some of you are rolling your eyes, I get it. I was just trying to take care of my stuff so don't bust my balls. I did some searching here about others using pressure washers with no issue, so I thought I'd be safe. I did a procedure similar to ChrisFix on youtube. I have done that procedure twice between my old 2012 FJ Cruiser and my wife's car. During my research here, I've learned about how sensitive these 4th gens are to water. Too many threads from creek crossers frying ECU's.

I'll keep this thread updated as I go. But I sure would take any input from anyone who has had or heard of similar situations.
Click to expand...

TheThunderRunner said:
Did you ever figure this out? I've been fighting 0121 and 0123 codes for like three years now.. Dealership hasn't even been able to figure it out.
Click to expand...

Just an FYI, the OP has been on the forum recently, BUT you need to get their attention if you want them to see your post/question and have them possibly reply to you, you need to do at least one of two things, quote them and or "mention" them either will then send them a notification and get their attention, this is how you mention them [MENTION=211099]Hog_runner[/MENTION] for the OP and [MENTION=144619]TheThunderRunner[/MENTION] , it's important when mentioning someone that you get their username exact and make sure there's no text or punctuation touching the "mention", so do the @ symbol and then the exact username with no space, and make sure you have a space/s before and after the mention to separate it from the rest of your post.

By my quoting and mentioning both of you, you both will get 2 notifications directing y'all to my post/reply.
 
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Forgot to update.

Short story: my timing belt slipped which is why I couldn't get a start. Not sure why that threw so many codes.

Long story: after 2 weeks of banging my head I called up a mechanic to come take a look. They had a nicer code reader and picked up codes that I wasn't getting on my cheaper model. They tested air, spark, fuel for me which was all OK. Still couldn't get a start though. Before I swapped in a new ECU I wanted the dealership to hook their reader up so I towed up there. After 2 weeks they still couldn't figure it out or get it to start. Then I had an epiphany - it was cold the morning I washed my engine bay and there was some freezing going on. When I tried to start it up that first time I wondered if the timing belt pulley was slick and slipped. Long shot but was out of ideas. Called the dealership and 2 hours later they called back saying it was out of time. Ran like normal after a retime. They didn't tell me anything about the codes, but i assume they cleared the codes from their reader and I haven't had one pop up since.
 
Hog_runner said:
A couple of weeks ago I was in a bind and had a shop replace my starter. They snapped the wires at the connector for one of my knock sensors so I went under and repaired that myself. So after that job I thought damn, I need to clean this engine bay up. Well, I did, and now I can't get to start. Been digging on the forums all day and can't find anything so I'd appreciate y'alls input.

Symptoms:
  • The truck turns over but gives up after the 3-4 second "auto" start.
  • P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
  • P0123 Throttle/Pedal Position Sensor/Switch A Circuit High
  • P2135 Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
My hunch is that I fried the throttle position sensor while cleaning my engine bay. According to DTC codes and referencing FSM (2006 ed.), looks like my options are replace the Throttle Body (to replace the throttle position sensor which is integrated to the TB), or replace the ECM if in actuality that is my problem. I think the ECM is fine though based on my ability to get readings thru my OBD scanner? I guess I'm confused why the car won't start even if the TB/Position Sensor is shorted/open/otherwise fried. I've been racking my brain all day. The FSM mentions a fail-safe mode if the throttle pos. sensor is out that would allow the truck to run in "limp mode" as I've seen it referenced here before. I guess maybe the intake could be out of sync and therefore not getting the correct air/fuel mixture?

Additional info/things I've tried:
  • charged battery
  • opened fuel cap, reinstalled
  • disconnected battery overnight
  • confirmed throttle body opens when accelorator is depressed
  • MAF picks up signal when air blown manually
  • ECM registers throttle opening position (thru OBD scanner)
  • I have gas :)
  • No blown fuses
I have not checked fuel delivery since I'm getting codes related to intake/throttle.
Click to expand...

Were you ever able to fix this issue? I'm running into the same codes.
 
AuSeeker said:
Yeah, I saw that after I posted, he's lucky it only slipped a little and didn't destroy the engine because of valves hitting pistons.
Click to expand...

That's what usually happens to me, I see it after. lol

Agreed on the TB, never heard of one slipping a tooth or two and don't see how it happens unless the tensioner is junk. Lucky I guess.
 
Been two youtube videos recently on 4.7L V8 timing belt failures and no engine damage, new timing belt installed and all is good.
 
rdruss said:
Been two youtube videos recently on 4.7L V8 timing belt failures and no engine damage, new timing belt installed and all is good.
Click to expand...

I have no doubt that could be the case in rare instances...but the crankshaft would of had to stop the instant the belt broke.
 
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