Codes 21 and 28

[jdub4.0]

Hey all, I have a 93 Lexus sc400 with about 130000 miles on it. Just had the ecu rebuilt by relentless Motorsports last week in hopes of getting rid of my check engine light. The car was having other issues as well but not anymore. I still have a check engine light and the only codes I’m getting is code 21 and code 28. I have also replaced both pre cat o2 sensors with Bosch o2 sensors(not universal ones). The car drives great but seems to run a bit rich. The check engine light only seems to come on when I rev it a bit past 2300 rpm’s. Sometimes it goes away at wot but always comes back. Any help is greatly appreciated.

 

[Tremor]

Have you cleared your codes by disconnecting the battery or pulling the main fuse and seeing if they return? A lot of the times the ECU does need to adapt to the running conditions and may take a few days to relearn it.

 

[gloverman]

Have you checked the voltages of the O2 signals? and the resistance of the heater circuits from the ecu? Checked the resistance of the signal circuits and check for possible shorts to ground in the loom?