DM914

I have checked the switch in the console and I have bought a replacement HGS transmission control module - The original module was defective wouldn't shift into 5th gear like it's supposed too. I pulled the module and the transmission would shift to fifth my question is if I replace the module HGS 008 545 26 32 do I need to do some kind of system reset for it to recognize the replacement unit or will it just function...

The reason I ask is I'm on my third module now and they all behave the same as the original - yet I have eliminated to the two potential issues, switch in the console and a defect in the actual transmission...

the car is 1990 SL300 - only has 74,000 KM so parts shouldn't be worn out....

DM914

Maybe I'll update the title a bit - when you replace the HGS transmission control module do you did to do any kind of computer or system reset for it see the NEW module ... my car will shift into fifth gear if I take the module out and I can see the switch at the console functions - I get continuity or an open circuit when I move the gear shifter from drive to 4th - but when module is installed car won't shift into 5th - all others work perfect...

Any more idea R129 guru's out there ? I've tried two modules and none is working thinking I'm doing something wrong..

bobterry99

I'll guess that this is not the case, but perhaps a stored fault code will prevent the module from engaging 5th gear. Otherwise, a replacement module needs no reset or adaptation to another vehicle.

I would read and erase any codes from diagnostic socket #13 (transmission controller). If you found one or more codes, drive the car; if still no joy, then read codes again and troubleshoot from them using the diagnostic manual: http://manual.startekinfo.com/manual..._1/content.jsp.

DM914

Thanks much - I have a diagnostic tool the little box with the flashy light - I'm having trouble finding the 38 pin diagnostic port - I've found the 8 pin drivers side inner fender well by the ABS controller - and I have found the 16 pin connector - left side at back where the hood switch is located...

the other 38 pin is a mystery - I've opened ever cover in the engine bay and can't find it. I read it's near the ECU cover but I can;t find that either - any help or a good photo of the location would be helpful - mine is '90 SL300 if that makes any difference .

DM914

diagnostic socket # 13 ? where would that be located...

bobterry99

The 38-socket and 16-socket connectors are mutually exclusive: if your car has one type, then it hasn't got the other.

Diagnostic socket #13 for the tranny is in the 16-socket connector.

DM914

No wonder I couldn't find the 38 socket connector! - it all makes sense now...

DM914

Ok - so Socket 16 testing socket 13 - with the ignition on and the car not running using my fancy OBD 1 reader - hold down the button for a couple of seconds to turn on I get three flashes ... so how do I find out what three flashes mean? - I can reset and drive car still does not shift into 5th ...

Once rest and without driving when I turn on I get one flash - which I understand is telling me everything is normal...

So where should I look next ...

bobterry99

The diagnostic manual I linked to in post #3 reveals that three flashes shows no engine load signal from the ignition control module. But if this code has not returned, then it may have been set during the Clinton Administration when the module was installed in another vehicle and should be disregarded.

If there are no codes, then I would go through the electrical test section of the diagnostic manual and check as many of the input signals to the controller as you can. If you find nothing wrong, then the improbable conclusion is that you have yet another faulty transmission control module.