: dtc pcm 0139 now what?

01-13-04, 12:14 AM
I was on my way to work last week and right when I went over a set of railroad tracks my service engine soon light came on. I pulled the code and it was pcm 0139. It turned off the next day, but came back on a day later at the same set of railroad tracks on my way to work. It turned off again, but now I'm wondering what that meant. I'm new to this site and am curious if anyone has any suggestions. Any help would be greatly appreciated. :D

01-13-04, 01:21 AM
Need the year and model please.


01-13-04, 08:15 PM
1997 de'ville

01-13-04, 11:32 PM
Ok...sounds like the pre cat O2 sensor has died.

Here the factory list on PO139-

The PCM provides a 0.45 volt reference signal to the oxygen sensor on CKT 1665. When the oxygen sensor is cold, below 200C (392F), the oxygen sensor signal voltage will be around 0.45 volt and the PCM will keep the system in Open Loop operation. When the oxygen sensor is warm, above 200C (392F), the oxygen sensor will swing from rich to lean rapidly, if the PCM is in good control of the air fuel mixture. DTC P0139 is designed so that if the oxygen sensor is slow to respond to changes in exhaust oxygen content, this DTC will set.

Conditions for Setting the DTC
Test Conditions
DTCs P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0141, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0300, P1133, P1134, P1139, P1153 and P1154 not set.
This test has not been completed yet this ignition cycle.
Low coolant level not present.
Ignition voltage between 9 volts and 16 volts.
Failure Conditions
Average time to change from rich to lean greater than .15 seconds.
Average time to change from lean to rich greater than .15 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC

The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
Use a scan tool to clear DTCs.
Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.
Diagnostic Aids

Do not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor. Refer to Engine Electrical for proper wire and connection repair techniques.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

Diagnose other DTCs first because they may be the cause of this DTC setting.

With the engine running warm, coolant at least 85C (185F) and at fast idle, the oxygen sensor voltage should rapidly swing above .60 volt and below .30 volt.

Checking if the oxygen sensor voltage is swinging between rich and lean very slowly, or not at all.

Checking for causes of oxygen sensor failure. If sensor is replaced without finding cause of contamination, contamination of new sensor may result.


01-14-04, 05:59 PM
My service engine soon light hasn't come back on, but what your saying is that my o2 sensor is probably gonna die soon? Is this something that I might be able to replace on my own. I usaully try to do things myself, but if it doesn't cost much more to have the dealership do it, I might consider going that route. Is this an expensive part? Thanks again for all of your help. I really appreciate it.:)

01-14-04, 06:27 PM
I once had an expirience where i went over a speed-bump too fast in a buick, and it turned the service engine soon light on, but not only that did it stall the engine too soon after. (Lol).

In this case, im going to have to say that it could be the sending/recieving wire not fully connected to the o2 sensor. When you go over that vibrating/extreme bump it probably jiggles the wire connexion and the car doesnt get a reading from that o2 sensor until you completely go over the bump and the wire has stopped moving.