Questions and Answers

Plymouth Acclaim Losses Power II Q. Dear Vince: In continuation of my lack of power dilemma for 1993 Plymouth Acclaim, 2.5 liter 4 cylinder, 83,000 miles, automatic transmission with A/C and P/S. Plymouth Acclaim Losses Power. Based on the information I provided to you, you helped me. I did not see the problem for a while. Then it happened again. This time I had more than half the tank full of gas. So the fuel pump must have been immersed.

I had doubt that maybe I was not reading the codes correctly. So I read again and asked my friend to help. After checking three times, we came up with following codes: 12, 21 and 55.

Recent work done was water pump replacement. So 12, battery disconnect, can be explained. Isn't the 21 code for O2 sensor? If so, could this be a bad O2 sensor and can it exhibit the symptoms I am experiencing? Is there any way I can test for bad O2 sensor? Could replacing the O2 sensor solve this intermittent problem? Any tips in replacing it, if that is what I need to do?

Also, I have never changed transmission oil at all. People are telling me that it's 11 year old car and the transmission is hold up with old oil. If I replaced it, I will loose my transmission and will have to end up replacing the transmission. So they are telling me to leave it alone. I don't understand the logic. Can you please advise me the last time?

As always, I thank you in advance.
Best Regards,
Naren

A. 21 Oxygen sensor signal. Neither rich nor lean condition is detected from the oxygen sensor input, or, 02 sensor shorted high. Oxygen sensor input voltage maintained above normal operating range.

This is how you can test the Heated Oxygen Sensor (HO2S).

CAUTION: Use a high impedance, minimum 10 Meg (10,000,000) ohm input impedance, Digital Volt Ohm Meter (DVOM) ONLY, when testing components on computerized vehicles.

1. Make sure the vehicle is at normal operating temperature. Run the engine at 2,500 rpm for three minutes with the transmission in PARK (A/T) or NEUTRAL (M/T).

CAUTION: To avoid damaging sensor, voltmeter must be set in VOLTS mode only, not ohms.

2. With engine OFF, connect the negative lead of the DVOM to engine ground. Set the DVOM to read DC VOLTS. Disconnect the oxygen sensor (O2S) electrical connector and connect the positive lead of the DVOM to the oxygen sensor signal wire, black/dark green wire.
3. Start engine. Create a lean condition for 10 seconds. Voltage should decrease to 0.2 volt or less and remain there.
4. Create a rich condition for 10 seconds. Voltage should increase to 0.8 volt or more and remain there.
5. If sensor fails to vary according to the test steps above, the sensor is defective.
6. Connect sensor and clear codes.