Quad Driver module 1 and 4 640 1640 670 1670 error

[spoiledred94]

A few weeks ago I got a SES ight and codes 640 and 670 (aka P1640 and P1670) . The code 1640 had been there mysteriously for months before the 1670 showed with no symptoms. Both of these codes reflect with quad driver module 4 and 1, respectively. Both of those quad drivers have the EGR valve in common as a device they control some part of. FYI the quad drivers an intregral part of the PCM that control and monitor various functions. My SES light came on when that 2nd code, the 1670 showed. Since the EGR valve was the only common device on the QDM's circuits I pulled it and replaced it. That didn't do it, the SES light was still on. I drove it for days and it still was on. I think it was post from here or BC that indicated the AC system so finally found a bad fuse under and in the Passenger dash and low and behold the AC fuse in there was blown. I replaced it and no more SES light! codes, both of them are gone.

I thought I'd post this as I did a lot of reseerch on this and there was a lot of questions but no complete answers

[Vernon001]

Hello, I am getting quad module driver #1 fault on my 95 Bonneville ssei. My understanding is the following 4 components are controlled by this. Low speed fan,TCC apply, Evap cannisters purge, and boost bypass valve. My actron scanner says code 0640.. The car is showing no symptoms and runs fine. The live data from the scanner indicates the Evap purge comes on, no transmission trouble and the supercharger is working. I replaced the low speed fan relay, but am still getting the check engine light. I read somewhere the brakes may be involved? Any thoughts or ideas would be appreciated. I am coming up for emissions testing..Thanks!