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The most common cause of Honda Civic P0128 code

What a Honda Civic P0128 means and what causes it

Honda has issued a service bulletin 13-044 to address a Honda Civic P0128 cooling system malfunction trouble code. The 13-044 bulletin applies to the vehicles listed below.

Normally, a P0128 code can be caused by a defective thermostat or a bad engine coolant temperature sensor. In this case Honda has identified a bad batch of thermostats. But you won’t be able to test these thermostats using the normal test procedures because the problem is caused by the jiggle pin. Honda P0128
A jiggle pin in a small round ball attached to a rod and strung through a hole in the outer thermostat plate. Car makers use a jiggle pin style thermostat mostly when the thermostat is mounted in a vertical versus horizontal position. However, sometimes you find them in engines with a horizontal mount thermostat. The jiggle pin allows any trapped air to flow past the thermostat and into the radiator.
This 13-044 bulletin states the jiggle pin in some vehicles may stick open delaying warm up.
2012 Civic With 1.8 L  – ALL Except CNG
2013 Civic 2-Door with A/T:
From VIN 2HGFG3B..DH500001 thru 2HGFG3B..DH511144
2013 Civic 2-Door with M/T With 1.8 L:
From VIN 2HGFG3A..DH500001 thru 2HGFG3A..DH530982
2013 Civic 4-Door with A/T:
From VIN 2HGFB2F..DH300001 thru 2HGFB2F..DH301244
From VIN 2HGFB2F..DH500001 thru 2HGFB2F..DH542439
From VIN 19XFB2F..DE000001 thru 19XFB2F..DE033981
From VIN 19XFB2F..DE200001 thru 19XFB2F..DE231338
2013 Civic 4-Door with M/T With 1.8 L:
From VIN 2HGFB2E..DH500001 thru 2HGFB2E..DH580337
From VIN 19XFB2E..DE000001 thru 19XFB2E..DE07553

Replace the thermostat with a new unit

Place the gasket onto the thermostat and make sure it doesn’t contact the jiggle pin. Mount the thermostat in the thermostat housing with the jiggle pin in the up position.

Honda thermostat

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