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Amedee, Former ASE Master Tech
Category: Car
Satisfied Customers: 26427
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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1992 Suzuki Sidekick 1.6L 16 valve and a M/T. Keep getting TPS code 21 and 45 for the idl

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1992 Suzuki Sidekick 1.6L 16 valve and a M/T. Keep getting TPS code 21 and 45 for the idle switch and voltage too high. I've put a new TPS on and no new change. Put a used known good throttle body assembly on and no change. Still the same codes and lacks engine power. Could it be a faulty ECM?

If you clear the two codes, which code comes back first?
Customer: replied 6 years ago.
Both at the same time. But the 21 flashes first, followed by 45.
Ok.. do they come back when driving or when the engine is at idle?
Customer: replied 6 years ago.
Not generally at idle. Most of the time while driving CEL comes on, all engine power lost (35 mph max). Come to a stop or let off gas the CEL will turn off/on intermittently.
Do you know what the tps voltage is at key on engine off?
Customer: replied 6 years ago.
Key on angine off, I unplugged the connector at the TPS and the blue/wht wire had 5.00v and the grey/red wire had 4.84v. So yes there is voltage
Ok.. excellent.

But what is the voltage leaving the tps sensor going back to the computer key on engine off?
Customer: replied 6 years ago.

Do you mean is voltage present at terminals B6 or B7 at the ECM with key on engine off?


NO.. what is the signal voltage from the tps back to the computer with the key on. You can check this right at the tps sensor by back probing the signal wire.
Customer: replied 6 years ago.

Key on engine off I back probed the grey wire which is the signal according to my diagram and it has 4.98v

Does the voltage vary when opening up the throttle?
Customer: replied 6 years ago.
Well, if this is the signal wire you are on..then this is going to be your problem. This signal should be at about .5 volt key on engine off and should go up close to 4.5 volts or so wide open throttle.
Customer: replied 6 years ago.
So would you recommend checking the signal wire for a short?
I would check to be sure that the TPS has a good ground. Also, be sure that the tps is installed correctly
Customer: replied 6 years ago.

I have already done those and they all checked ok. I stated that in my question above.

Then your new TPS sensor is bad
Customer: replied 6 years ago.
This will be the third 'bad' TPS sensor. The original one with the car, the new one and now the used one on the throttle body assy. I have adjusted each one according to the haynes and chiltons manuals I have on the car. I don't doubt you at all, but do you think all three could be faulty causing the problem I have?
From what you are telling me.. yes.. it is either that or you have not done all of the checks correctly.

Does the voltage change on any of the wires as you open the throttle up?
Customer: replied 6 years ago.
Only on the blue/wht wire, it changes from 5.00v to 0.15 then just stays on 5.00v. On my diagram the blue/wht wire is the idle swtich wire to the ECM.
Right.. mine too.

One of these are supposed to go from about a half of a volt up to 5 volts.
Customer: replied 6 years ago.
I agree. I think one more adjustment attempt is in order. I will try to get the signal wire to read correctly. Thank you for your help.
You bet!

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