For the record I have searched the forum and google. I was just hoping to have someone else with the same problem chime in.

My sister has an 08 HHR with the 2.2L engine. She recently lost 4th gear. It still has 1-3 gears. I had her go to O'Reillys and borrow a code reader.

Here are the codes she pulled.

P0128 - Coolant Temp Below Threshold - Needs a new thermostat but gauge occasionally stops displaying temp
P0420 - Change cats already and installed new O2 sensors front and back, can hear an exhaust leak, I suspect that is the culprit
P0700 - Transmission control system mil request
P0751 - Shift Solenoid 'A' Performance or Stuck Off
P0752 - Shift Solenoid 'A' Performance or Stuck On
P0974 - Shift Solenoid 'A' Control Circuit High

This is just a different set of codes that I haven't seen with anyone else's problems. I still believe it is just the shift solenoid A thats bad, 2 GM dealers want to replace entire trans and 1 of 2 trans shops want to replace entire trans. The other one wants to replace just the shift solenoid a. However we had this specific shop rebuild a 4l60 that didn't even last a year before it lost 3rd and 4th gear.

Can anyone provide some input on the subject. Thanks

 

Shift solenoid 'A' has a problem. I don't know much about transmissions. But I think you have to pull the trans to get to it, they may be saying cost effectiveness.

P0128 means replace the t-stat.

P0420 can be a PIA, What do you mean exactly " Change cats "? Exhaust leak rarely causes it.

 

Before I attempt any advice, how many miles are on this car ?

 

P0420 can be a burnt wire, loose electrical connection at either O2 sensor

 

98SilvZ71, it depends on how many miles regarding to replace/fix.. If you replace the solenoids I would recommend replacing them all. they are like 10-15 bucks each and the labor and expense is in removing the trans not replacing the actual solenoids.. I had bad solenoids, but I had over 200k on the car, I replaced my engine and trans as a unit with a donor HHR with 37k miles on it.. IMO if you have over 150K on the car, u might want a new or used low mile unit to replace it, but if the trans doesn't have that much, see what it will be to replace the solenoids..

 

The ECT sensor being out of range will inhibit the transmission from going into 4th and Lock up. Fix that and see what happens.

 

My '08 had a shifting problem and had a code for solenoid. The dealership had the trans rebuilt. Only had 35k miles on mine.under warranty.