Code 13. Clean the connector to the coolant sensor. You can use a dental pick, sand paper. If this doesn't work remove the sensor and clean thoroughly.
Code 34. On our cars that have high mileage it's not uncommen for that sensor to go bad. First try and clean the connector and if that doesn't work there is a by pass you can use to delete the detonation sensor since it's a PITA to replace while the engine is in the car.
http://zhome.com/ZCMnL/PICS/detonati...ionSensor.html