check engine at 60mph only

[grilledcheese]

Hi all. Recently purchased an 85 2wd van. The check engine comes on after a few miles and only at around 60mph. When I slow down, it turns off. I am getting code 5, which indicates oxygen sensor. I think I will start with replacing that but was wondering if anyone else has experienced this. Thank
you.

[llamavan]

See THIS THREAD (https://www.toyotavantech.com/forum/showthread.php?4508-O2-sensor-(84-87)). In a nutshell, replacing the O2 sensor should take care of it.

Gwen

[JPERL]

Check to make sure the 02 sensor wire is not broken at the connector. Its not so much the speed you are going but rather the RPM if you maintain a steady 2000RPM for 2 minutes the check engine light will come on if the 02 sensor signal has an open circuit (broken wire) some times the break is partial so examine the wire closely at the connector.

To test this theory out try fluctuating the RPM every minute or so and you will find the check engine light does not illuminate. This also coincides with the testing procedures of the 02 sensor in the service manual where it says to hold a steady RPM of 2K or more for 2 minutes.

You will want to get this repaired as gas mileage will be crappy because the ECU will default air fuel mixture to rich with no input from 02