Looked at my service manual.. thought you'd like to read this
@Elkins45
The difference between is that P0123 indicates the sensor voltage was higher than 4.535V and P0121 confirms that was out of range voltage. Basically saying the same thing but confirming each other.
I've cut/pasted from the service manual.. Again check the gas pedal sensors (dirty, not connected, etc).. If those check out the throttle body TPS has gone.. Odd because I don't remember this being a common problem.
I'm also wondering if you check the throttle plate for sticky deposits, cleaning it with some MAF sensor cleaner (if you're not taking it off the manifold, safe for plastics).. If you use throttle body cleaner, do not spray the throttle body throat, acetone will melt the plastic intake manifold! Use it on a sponge swab or cotton swab first, then clean. If the throttle body jammed because it was sticky, the TPS could see this as a fault.. Trying to look at everything before you replace parts!
"P0123-
Output voltage of VTA1 4.535 V or more for 2 seconds
when accelerator pedal depressed
(1 trip detection logic)
Problem area :
• TP sensor (built into throttle body)
• Open in VTA1 circuit
• Open in E2 circuit
• Short between VC and VTA1 circuits
• ECM
DESCRIPTION
These DTCs relate to the Throttle Position (TP) sensor.
The Throttle Position (TP) sensor is mounted on the throttle body, and detects the opening angle of the
throttle valve. This sensor is a non-contact type, and uses Hall-effect elements, in order to yield accurate
signals, even in extreme driving conditions, such as at high speeds as well as very low speeds.
The TP sensor has 2 sensor circuits. One circuit sends the VTA1 signal. The other circuit sends the VTA2
signal. VTA1 is used to detect the throttle valve angle and VTA2 is used to detect malfunctions in VTA1.
The sensor signal voltages vary between 0 V and 5 V in proportion to the throttle valve opening angle, and
are transmitted to the VTA terminals of the ECM.
As the valve closes, the sensor output voltage decreases and as the valve opens, the sensor output
voltage increases. The ECM calculates the throttle valve opening angle according to these signals and
controls the throttle actuator in response to driver inputs. These signals are also used in calculations such
as air-fuel ratio correction, power increase correction and fuel-cut control.
MONITOR DESCRIPTION
The ECM uses the Throttle Position (TP) sensor to monitor the throttle valve opening angle. There are
several checks that the ECM performs to confirm the proper operation of the TP sensor.
• A specific voltage difference is expected between the sensor terminals, VTA1 and VTA2, for each
throttle valve opening angle. If the difference between VTA1 and VTA2 is incorrect, the ECM interprets
this as a malfunction in the sensor, and sets a DTC.
• VTA1 and VTA2 each has a specific voltage range. If VTA1 or VTA2 is outside the normal operating
range, the ECM interprets this as a malfunction in the sensor, and sets a DTC.
• VTA1 and VTA2 should never be close to the same voltage level. If VTA1 is within 0.02 V of VTA2, the
ECM determines that there is a short circuit in the sensor, and sets a DTC.
If the malfunction is not repaired successfully, a DTC is set 2 seconds after the engine is next started.
FAIL-SAFE
When any of these DTCs, as well as other DTCs relating to ETCS (Electronic Throttle Control System)
malfunctions, are set, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts the current to
the throttle actuator off, and the throttle valve is returned to a 6.5° throttle angle by the return spring. The
ECM then adjusts the engine output by controlling the fuel injection (intermittent fuel-cut) and ignition
timing, in accordance with the accelerator pedal opening angle, to allow the vehicle to continue at a
minimal speed. If the accelerator pedal is depressed firmly and gently, the vehicle can be driven slowly.
Fail-safe mode continues until a pass condition is detected, and the ignition switch is then turned off."
