Hello, Im stuck on a problem and its been bugging me the last week. My car is an 87 supra 7mge a340e (auto). I just did a new head gasket and after I put it all back together I went to start it and it came back with code 52 and 51. I know 52 is the KS and 51 is the ECU has no "IDL", "NSW" or "A/C" during diagnostics. The car starts and idles fine, but when it revs it stumbles slightly, revs up fine, returns and dips to 800 rpm then returns to 1000-1100 rpm. Keep in mind that I never had these codes before the car was taken apart, nor these problems. So I tried to fix code 52 with a rewire and a new sensor and it still comes back with a fault code (that was expensive). I also tried to clean the terminals at the tps and inspect all the wires going to the tps for code 51 and have had no luck with that either. Im aware of all the threads on the forums about both codes but none have given me a solution to this problem. My question is is there something that can trigger both codes at the same time? And, is there something i could've missed when putting everything back together? Thanks for any replys!
1987 supra 7mge Code 52 and 51
- Thread starter suprasteveo
- Start date
Tps could be out of adjustment or it needs to be replaced. I had one fail directly after changing the head gasket one time.
For the 52 how did you do the rewire. Did you ground one side of the shielding like stock?
For the 52 how did you do the rewire. Did you ground one side of the shielding like stock?
I grounded both sides of the shielding (I believe the write up said it didn't matter). Could this affect the signal from the sensor? Also, I just did the tests on the tps and found the idle switch (pins E2 and IDL) is always ON regardless of whether or not the throttle is open or not... I also checked pins E2 and VC and recieved a reading of 1.777ohms. Is this enough proof to replace the sensor or is there something else I can try before spending another portion of my paycheck on my car again? Thank you for the reply BTW!
A few observations:
1) Shielding should be grounded at one end only to prevent ground loops. You can do it at the ECU (it's done at the manifold from the factory.)
2) Dunno what you mean by "on" but a constant short between IDL and E2 will *prevent* a TPS related code 51 from being triggered. Therefore you're either doing it wrong or the code is related to one of the other two causes. Be careful when selecting which TPS pins to measure...there is a difference between the GTE and GE as shown in the manual.
3) E2 - Vc: Again, be sure you're on the correct pins. Also be sure you're using/interpreting the meter correctly
Lastly, you really ought to be measuring voltage during these tests...preferably at the ECU. That way the wiring gets checked.
1) Shielding should be grounded at one end only to prevent ground loops. You can do it at the ECU (it's done at the manifold from the factory.)
2) Dunno what you mean by "on" but a constant short between IDL and E2 will *prevent* a TPS related code 51 from being triggered. Therefore you're either doing it wrong or the code is related to one of the other two causes. Be careful when selecting which TPS pins to measure...there is a difference between the GTE and GE as shown in the manual.
3) E2 - Vc: Again, be sure you're on the correct pins. Also be sure you're using/interpreting the meter correctly
Lastly, you really ought to be measuring voltage during these tests...preferably at the ECU. That way the wiring gets checked.
Ah, I suppose the code wouldn't be thrown. I'll have to look at the manual to see the difference in the pins between the GE and GTE, I'm glad I saved my money. Thank you for clearing some of this up for me! I'll do some tests and see what I can find.
'Alright, so I did some more checks on the TPS and found that E2 and VC was still maintaining at 1.777 ohms regardless of where the tps is positioned (every test was done as per the manual spec). As is the same kind of story with the E2 to VTA, and E2 to IDL. I picked up a new TPS today for $90 and code 51 has vanished.
But now I need to figure out code 52. I've tested the sensor with an oscilloscope and found when I rev the engine it goes from around 15-30mv (idle) to around 350-500mv depnding on the amount of throttle I give it. I was planning on re-wiring the KS a little later today to see if I could make a dent in it, but was wondering if the knock sensor itself could be the problem. Is there a section in the manual that might give some insight to whether my tests are in spec or should I put the time into rewiring the sensor again?
But now I need to figure out code 52. I've tested the sensor with an oscilloscope and found when I rev the engine it goes from around 15-30mv (idle) to around 350-500mv depnding on the amount of throttle I give it. I was planning on re-wiring the KS a little later today to see if I could make a dent in it, but was wondering if the knock sensor itself could be the problem. Is there a section in the manual that might give some insight to whether my tests are in spec or should I put the time into rewiring the sensor again?
I did that and still have the code.
I decided to also tested resistance from the block to the housing of the sensor itself and got 2.5ohms. I believe this is a bit excessive for such a sensitive signal coming out, so I ran a wire from the negative battery terminal down to the sensor and just wrapped it around the base (obviously not permanent) and reduced resistance down to 1ohm. And yet still yet...no bueno. Still looking for solutions.
I'm thinking there may have been a cold solder on one or both sides of the rewire I did so I'm gonna check there next. I appreciate your both your guys input. Thank you!
I decided to also tested resistance from the block to the housing of the sensor itself and got 2.5ohms. I believe this is a bit excessive for such a sensitive signal coming out, so I ran a wire from the negative battery terminal down to the sensor and just wrapped it around the base (obviously not permanent) and reduced resistance down to 1ohm. And yet still yet...no bueno. Still looking for solutions.
I'm thinking there may have been a cold solder on one or both sides of the rewire I did so I'm gonna check there next. I appreciate your both your guys input. Thank you!
No, I soldered the signal wire to the a 18 gauge speaker wire and grounded it near the ecu. I made sure not to have any interference with the signal wire.
Oh sorry, I had the shielding wire grounded near the ecu NOT the signal wire. The signal wire I soldered with the clear wire out of the ecu.
I decided to re-solder the ecu end of the knock sensor wire (spur of the moment thing), I also switched ends on the ground wire so now its grounded on the intake manifold instead of next to the ecu.
Once I did that, I tried to fire up the car and it wouldn't fire up. It took several tries for it to reluctantly start to idle at 550-600 rpm and stall intermittently. Its trowing a code 52 (no surprise) and a code 22 which has to do with the temp sensor and cold starts (it was right around 30 degrees when I tried to fire it) I believe.
I checked to make sure I hadn't messed with any other wires when I re-soldered the knock sensor, and everything looks good.
Once I did that, I tried to fire up the car and it wouldn't fire up. It took several tries for it to reluctantly start to idle at 550-600 rpm and stall intermittently. Its trowing a code 52 (no surprise) and a code 22 which has to do with the temp sensor and cold starts (it was right around 30 degrees when I tried to fire it) I believe.
I checked to make sure I hadn't messed with any other wires when I re-soldered the knock sensor, and everything looks good.
A 22 indicates a short or open in THW. Since the ECU defaults to a hot coolant parameter in that case it's no surprise cold starts will be difficult.
I understand now. I ohmed out the wire from the the coolant temp sensor pin THW back to the ecu and found that both ends were exactly the same so the wiring is good. I also did a comparison to the chart from page 113 of the fsm to the sensor itself and found that that was fine. Also, it's not throwing the code anymore (probably should've said that at the beginning). Probably was a crap connector that started working when I disconnected and reconnected it.
Back to code 52, I drove the car a couple of times today and the timing of the engine light to come on varied. I know the wiring is good, Ecus usually don't go bad, and the sensor's new. Losing hope and patience.
Back to code 52, I drove the car a couple of times today and the timing of the engine light to come on varied. I know the wiring is good, Ecus usually don't go bad, and the sensor's new. Losing hope and patience.
Well I'm trying. That's all I can say.
Is there any tests to verify that the sensor on my car is working properly in terms of output? I've been scouring the TSRM to find something on this but have turned up blank. What sort of range should I be looking for in terms of mv when I do this on an oscilloscope? Last time I did this the sensor produced a signal that came up to about a half of a volt at 5500 rpm and returned back to around 15-30mv at idle. Yay or Nay?
Sorry I've been confusing and impatient, just want my baby to run like a champ again. It's just frustrating. Thanks for all the input and advice though!
Is there any tests to verify that the sensor on my car is working properly in terms of output? I've been scouring the TSRM to find something on this but have turned up blank. What sort of range should I be looking for in terms of mv when I do this on an oscilloscope? Last time I did this the sensor produced a signal that came up to about a half of a volt at 5500 rpm and returned back to around 15-30mv at idle. Yay or Nay?
Sorry I've been confusing and impatient, just want my baby to run like a champ again. It's just frustrating. Thanks for all the input and advice though!