P1781 and p0700 codes only
Are there any plugs that could have been left unplugged? We just had the timing belt idler pulley grenade and bend the valves. Professional reworked the head. All valves are new and we are not getting any misfire codes. We are getting p0107 map sensor code. MAP sensor checks good as voltage varies between 4.8 and 1.2 volts when throttle is opened and closed with engine running When started the rpm goes to about 3000 to 3500 and drops back in a few seconds. The engine runs Great and Smooth. Idles at just under 1000 RPM. Has Lots of Power! Only will not go into 4th gear (automatic) Limp Mode? Codes are p0700, p0107 and p1781. Please Help
Cars & Trucks - Chevrolet - Aveo - 2004 Chevrolet Aveo
Answers & Comments
The Code 700 is a generic transmission Code and in some cases may relate to Emissions problems relating to transmission performance. Beyond the generic Code, a better scanner will show the specific defect.
The Code 1781 is a hodge-podge of defects. Found a GM TSB on valve seals and valve replacement. It listed (By serial#) a replacement sequence where on some production numbers only the Exhaust valves needed to be replaced, and on others all valves needed replacement. All the valve seals needed replacement regardless of serial#. Perhaps this is a hold-over from your original problem.
The Code 1781 is a misfire Code due to Valve seals. It is also listed as a condition where the Engine Torque signal is wrong. And also a condition where the ECM and TCM are not communicating.. Can't say why so many different problems tied to 1 code.
The Code 107 is as you said is a Map sensor Code. Many makers operate this warning the same way. You are correct that your MAP is probably good. For some reason, the makers blame the MAP for the problems of the devices which report to it. From the O2 sensors back through the throttle positioner and all airflow occurring after the airflow passes the MAP. If the measurements do not meet the settings that are permanent at that "appliance", then a MAP code will show. What you need to do is examine the downstream parts to determine why they do not conform. Even a intake gasket leak will affect the manifold pressure.