look up: OBDII Diagnostic Trouble Codes
Although I haven’t experienced this issue thus far, apparently a few of the thermostats that Mazda has installed (the majority of the cooling system is Mazda MX-5, so this is not the Fiat thermostat used on the 500, although some of those have issues as well) onto our Fiat engines have been troublesome (sticking in the open position or opening too soon), which results in the engine warming up to normal operating temperature too slowly. There are a few clues, that you may observe eventually, that you may have one of these faulty thermostats:
- the blue engine coolant light (which triggers OFF at 130° F) remains ON for longer than about 5 – 7 minutes after starting your engine that has been off for more than an hour.
- the coolant temperature gauge takes more than 5 – 7 minutes to get to normal operating temperature.
- the CEL (Check Engine Lamp) is ON, and the error code P0128* will come up if an OBD-II diagnostic tool is hooked up to your vehicle.
Consider this as an inconvenience issue rather than a critical issue, but don’t ignore it either. This is obviously a warranty item that your dealer will fix for you, but the thermostat is very difficult to get to (at the rear of the engine adjacent to the firewall), and they seem to be on back-order, so you are advised to ask the dealer to pre-order the following parts and verifying their arrival (on hold in your name) prior to your service appointment for the repair, so that your vehicle isn’t kept for a couple of weeks waiting for said parts:
- replacement thermostat (Part # 68320858AA) >> different part # than the thermostat Mazda originally installed. Item #6 in parts diagram:
- vacuum pump gasket (Mopar # 68140726AC) >> in case the vacuum pump needs to be removed in order to access the thermostat.
- Mopar # 68334695AA Antifreeze / Coolant
It is OK to drive the vehicle in this condition while you are waiting for your service appointment, but as the manual advises you to do when the blue coolant lamp is ON, go easy on “engaging the turbo” 😉 for the longer duration that that lamp is illuminated. Some with marginal thermostats have had good luck preventing the error code P0128 trigger, by engaging the AC after starting the engine, the extra load aiding in warming up the engine quicker.
Here are the specs on our Mazda-sourced thermostat:
Apparently, Fiat is currently advising dealers to flash the 124 Spider’s ECU (also known as the Power Control Module (PCM) Part # 68231492__) to firmware level AI, to alter the engine operating temperature vs. time algorithm somewhat, so that the CEL (and the P0128 trouble code*) isn’t illuminated for marginal thermostat behavior, especially for North American market thermostats, which are spec’d differently. Obviously, this is not a cure for truly defective thermostats though.
* P0128 Trouble Code: Indicates that the coolant temperature has not achieved the required thermostat regulating temperature (engine operating temperature) within a specified amount of time after starting the engine.