Scan Lab: AUTEL MaxiSys MS906 MAX

 Gonna change things up just a bit and actually do some diagnostics this time. This 2013 Accord was here for a valve cover gasket but I also noticed a tire monitor light on. After checking the tire pressures and all were fine, I thought to enter the TPMS (Tire Pressure Monitor System) data and see what it had to say. I found this Accord has no TPMS. It doesn't even have tire pressure sensors. It uses the ABS module to calculate tire pressure as it monitors tire diameter changes. Now when you can look into TPMS data you can see how much tire pressure the system is reading from each pressure sensor but not so here. I scanned instead for codes in the ABS and found two, one said I had a tire with a different diameter in left front or right rear and I had a low tire pressure in one tire. I couldn't see which tire was "low tire pressure" as it has no data for that in the data stream. It also isn't clear about that left front or right rear though I suspected one of those triggering both codes. That VSA System Malfunction would probably be related to the ABS codes. VSA is the vehicle stability assist system which of course would be concerned with a wrong diameter, low tire. The EPS is the electric power steering module which also needs to know your wheel speed, so isn't trusting the wheel speed sensor of a tire that seems to be out of range and triggering these codes. Now I had checked all the tire pressures and they were fine. Next I wanted to make sure all the tires matched in size and brand, which they did. 

There is a bit of forensics involved in car repair so best I could make sense of the evidence was that perhaps this did at one time have a low tire, which could trigger all those codes, but the low tire had been repaired of filled and was no longer low. This would mean that perhaps the system simply needed to be re-calibrated which can be done via the central display in the car. Use settings, scroll to vehicle settings, then choose TPMS calibrate and re-calibrate. The car needs to drive some distance at beteen 30 to 60 mph and will reset. 

The low tire light went out and the codes cleared. All fixed. Previous to the calibration the codes would not clear but remained in permanent codes. 

Let's move on to the 4Runner with cat efficiency codes, P0420 and P0430. 

Now a cat efficiency code will usually set then a cat monitor is too active,. A fully warmed vehicle with a working cat should see the rear O2 slightly rich at 2000 rpms and fairly steady. If it is reacting to the fuel mix too actively the computer determines the cat isn't working properly and you get the code. But here if I look at the O2 monitor test results for each sensor I can see they are failing due to slow response time. 

Now when I graph the rear sensor signals I can see that I do indeed need cats. That bank 2 sensor is slightly rich and fairly steady all right but that isn't quite near enough to the 0.65 I would expect. The bank 1 is switch too much rich to lean though the activity is indeed slow. So far it looks like I need cats AND rear O2 sensors. If these rear sensors were working properly, as new ones will they will just more quickly say, hey these cats aren't working. 

Only one thing left to check. I want to see that the front O2 are showing me a good fuel mix going into the converters. Technically this 4runner is using Air/Fuel ratio sensors in front of the cats. You monitor these by looking at lambda. Lamda is 1.00 and lets you see if the system has good fuel ratio control as it stays near 1.0 with only very slight variations. We have good fuel control here. 

Thanks for reading.

Kenny@GGAuto.Repair