DTC 22 - "Throttle Position Low"
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Racer
Joined: Nov 2010
Posts: 328
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From: Sacramento CA
DTC 22 - "Throttle Position Low"
I am getting a code of DTC 22 - "Throttle Position Low" when I hook up OBD 1 to my 1990 Corvette. I went out and got a new Throttle Position Sensor and replaced the old one with it. Then I disconnected the battery to reset the codes stored in the computer. I hooked up OBD 1 again and I still got the DTC 22 code. The problem that my car is having is a rapid jerking motion during initial acceleration from a dead stop. When I let the car roll out of a dead stop and then hit the gas there is hardly a problem. Any assistance on this issue would be much appreciated.
Instructor
Joined: Jun 2008
Posts: 173
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From: Norman OK
Code 22 means the TPS circuit is voltage is low.
The TPS is nothing more than a variable resistor which changes by throttle movement.
The TPS gets a 5 volt reference voltage from the ECM on the grey wire Pin C and sends the "adjusted voltage" signal back to the ECM on the dark blue wire (Pin B) to determine fuel delivery.
With a code 21 or 22, the ECM goes to default values to deliver fuel.
With a voltmeter, with key on, backprobe Pins A and B at the TPS and check for .56 volts (+/- .07).
If it is there, open the TB to wide open throttle and look for over 4.5 volts.
If voltage is not there, with the Code 22 history, you may have a wiring problem on the dark blue or grey wires, a bad TPS connector... or no 5V from the ECM.....
The TPS is nothing more than a variable resistor which changes by throttle movement.
The TPS gets a 5 volt reference voltage from the ECM on the grey wire Pin C and sends the "adjusted voltage" signal back to the ECM on the dark blue wire (Pin B) to determine fuel delivery.
With a code 21 or 22, the ECM goes to default values to deliver fuel.
With a voltmeter, with key on, backprobe Pins A and B at the TPS and check for .56 volts (+/- .07).
If it is there, open the TB to wide open throttle and look for over 4.5 volts.
If voltage is not there, with the Code 22 history, you may have a wiring problem on the dark blue or grey wires, a bad TPS connector... or no 5V from the ECM.....
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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Instructor
Joined: Jun 2008
Posts: 173
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From: Norman OK
.35 appears low, but before you go for an ecm, I would check voltage at Pin C of the TPS with the key on. It should be 5 VDC.
When you backprobe pins A and B, you are reading the TPS "adjusted" voltage which is being sent back to the ECM.
If you are below .54 while backprobing A & B and you have a known 5 volts coming in to the TPS, then you have a bad new TPS.
If you have less than 5 VDC coming in on Pin C, then you may have a bad or corroded pins at the TPS connector, or high resistance in the grey wire between the ECM and TPS, or dirty/corroded ECM connector pins.
