03 caravan showing codesP0123 and P0121. Can anyone help me with this. The van is not shifting gears properly. Thanks!
P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance
The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up. The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code.
Symptoms of a P0121 trouble code could include:
Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
Intermittent stumble on acceleration or deceleration
Blows black smoke on acceleration
A code P0121 may mean that one or more of the following has happened:
TPS has intermittent open or short internally
Harness is rubbing and causing an open or short in the wiring
Bad connection at the TPS
Bad PCM (less likely)
Water or corrosion in connector or sensor
1. If you have access to a scan tool, see what the idle and WOT (wide open throttle) readings are for the TPS. Check if they're close to the specifications mentioned above. If not, then replace the TPS and re-check.
2. Check for an intermittent open or short in the TPS signal. To do that, you can't use a scan tool. You'll need an oscilliscope. The reason is because scan tools take samplings of many different readings over just one or two data lines and can miss an intermittent drop out. Hook up your oscilliscope and watch the signal. It should sweep up and down smoothly with no drop outs or spikes.
3. If no problems were noticed, perform a wiggle test. Do this by wiggling the connector and harness while watching the pattern. Does it drop out? If so, replace TPS and re-check.
4. If you have no TPS signal, check for 5 Volt reference at the connector. If it's present, check the ground circuit for open or shorts.
5. Make sure the signal circuit isn't 12V. It should never have battery voltage. If it does, trace circuit for short to voltage and repair.
6. Look for any water in the connector and replace TPS as necessary.
P0123 Code - Throttle Position Sensor/Switch A Circuit High Input
A P0123 code means that the the car's computer has detected that the TPS (throttle position sensor) is reporting too high a voltage.
Symptoms may include:
other symptoms may also be present
A code P0123 may mean that one or more of the following has happened:
TPS not mounted securely
TPS circuit short to ground or another wire
Damaged computer (PCM)
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, carefully inspect all wiring and connectors that lead to the TPS. More than likely the problem is with the TPS wiring. Check the voltage at the TPS (refer to a service manual for your vehicle for this specific information). If the voltage spikes or is too high (over 4.65 volts with key on, engine off), then that is indicative of a problem. Carefully trace each wire from the TPS wiring harness to check for breaks, rubbing against other components, etc.
Apr 19, 2012 |
2003 Dodge Caravan