Because thermal efficiency of electronically controlled diesel engine is higher than that of gasoline engine, heat loss to cylinder wall is lower. This enables electronically controlled diesel engine to generate high power and have high fuel efficiency.
However in other point of view, due to low engine coolant temperature, heating efficiency lowered then, driver is unsatisfied with the heating. To cope with this situation, PTC heater is installed in coolant line and it raises heating efficiency and raise coolant temperature.
ECM activates heater relay 1 and 2 when engine coolant temperature is below 70? and engine speed is above 700RPM.
? Heater relay operation inhibited condition : engine coolant temperature above 70?, engine speed below 700RPM(to prevent battery discharge)
P1634 is set when excessive current or "0"A is detected in heater relay control circuit for more than 1.0 sec. at heater relay operating condition. This code is due to 1)open or 2)short to battery or ground in heater relay control circuit or 3)component problem.
Item
Detecting Condition
Possible Cause
DTC Strategy
Voltage monitoring
PTC heater relay #1 control circuit
Heater relay component
Enable Conditions
IG KEY "ON" (monitoring only performed at relay operating condition)
Threshold Value
Short to battery
Diagnostic Time
1.0 sec.
Fail Safe
Fuel Cut
NO
EGR Off
Fuel Limit
Check Lamp
Heater relay
coil resistance
PTC heater
operating temperature
operating condition
52±5? (20?)
Coolant temp. beolw 70?
(Intake air temp.below 5?)
Engine speed above 700RPM
(Battery voltage above 8.9V)