Scanmaster afr 19.9

Haynesie

Member
Joined
Apr 28, 2004
Hello,

I’ve had my wideband hooked up to my powerlogger which feeds my scan master g for about 6 months or so. In the last week or so the scan master will display the AFR readings fine, and then ten minutes or so into a drive it gets stuck on 19.9 and there is as “.” that shows up on the lower left of the scan master screen…then eventually goes away. Occasionally the afr readings will come back on but it’s not really reliable.

Any ideas what could be going on? All other signals show up just fine on the scan master.
 
Sensor going bad probably. I had this problem recently, and found it was the sensor. The longer the motor idled, the leaner the sensor would read until it wouldn't show anything on the AEM gauge. It's in the location that Jason at RJC welds in the o2 bung, and I think it may be a little too close to the turbo(if you have a big turbo), and is causing the sensor to fail prematurely. My '86 has a TE44 with RJC downpipe and has had the same WBo2 sensor for 9 years with no problems, but my '87 had a 6262(now 6466) with the RJC downpipe and goes through sensors pretty often.
 
check the wiring connections. A car would not even idea at 19.99 AFR either. So probably wiring or sensor issue
 
Cool...thanks yeah I was hoping it wasn't the sensor...since they are not cheap (this is a PLX wideband) and their site lists the sensor for $100....
 
yea the sensors arent cheap. Check Amazon, ebay autozone etc too. I last paid $75 but that was a while ago.
 
Since you have a Powerlogger, take note of the o2 volts next time it happens. Compare that to what the wideband says. My o2v would be in the .800s, yet the wideband would read in the 15s and 16s, ect... Once the motor was warm and when at an idle, I could literally watch the WBo2 going leaner and leaner until it wouldn't give a reading anymore...all while the o2v stayed constant.
 
Make sure the wideband controller is grounded to an engine ground (the same as the ECU is grounded).
 
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