Grid heater ?'s

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Black98cummins

Black98cummins
Joined
Aug 7, 2010
Messages
72
Alright so my grid heater doesn't work i thought it was the relays but they r good bc i can trip them by runnin wires from small posts on bottom of relays to a power an a ground an the grid heater will kick on so my question is what exactly r the two little wires on the bottom of the relay an where do they run to and what sends the signal to trip the relay to turn on the grid heaters is it the PCM or ECM and would a simple reflash possibly fix it or is it gonna have to be replaced my wait to start light functions normally and i can wire a switch to ground the relays to activate the grid heater but I'd rather have it function the way it should and not have the hassle of using a switch Iv searched for this everywhere an nothing any help would be apreciated
 
it runs off the ecm.... the wires are shown in a chiltons book for your truck... dont know what will fix it for you
 
Does it show where they run do they both run directly to ECM and is one a signal an one a ground or what thanks
 
IIRC, both come from the ECM. Check to make sure you have 12V at the relay post coming from the battery (the two wires have fuseable links in them).
 
I have 12volts coming from battery to the relays where r the fuseable links I'n the two small wires running to the ECM
 
doesnt the ecm get told to power them up by reading the iat temp probe in the intake?
 
Yes that's what tells the ECM how long to kick em on by how cold or warm the intake temperature it but as far as i know my iat is good
 
fuseable links are in the two wires coming from the battery. If you have 12V on that terminal at the relay then they are good.
 
Ok i believe my PCM isn't sending signal to activate the solenoids so do i have to replace my PCM with a brand new one an have it vin programed or can i get a used PCM off of another automatic an it will be fine to install it
 
There is a temp sensor under the driver side battery tray, I thought this is what controlled grid heaters?
 
I don't think the Battery temp sensor is used at all for intake heaters, however I recall the engine coolant temp sensor is also used for high idle functions and 3 cyl idle functions. Maybe it is used as well for the intake heaters? Is your coolant temp sensor working?

This is from the service manual:

OPERATION
The Engine Control Module (ECM) operates the 2 heating elements through the 2 intake manifold air heater relays. Refer to Powertrain Diagnostic Procedures for an electrical operation and complete description of the
intake heaters, including pre-heat and post-heat cycles.


INTAKE AIR TEMPERATURE SENSOR
OPERATION - DIESEL
The IAT provides an input voltage to the Engine Control Module (ECM) indicating intake manifold air temperature. The input is used along with inputs
from other sensors for intake air heater element operation, for engine protection, fuel timing and fuel control. As the temperature of the air-fuel stream in the manifold varies, the sensor resistance changes. This results in a different input voltage to the ECM.

BATTERY TEMPERATURE SENSOR
OPERATION
The BTS is used to determine the battery temperature and control battery charging rate. This temperature data, along with data from monitored line
voltage, is used by the PCM to vary the battery charging rate. System voltage will be higher at colder temperatures and is gradually reduced at warmer temperatures.
The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled, depending upon BTS input (for example, disable purge and enable Leak Detection Pump (LDP) and O2 sensor heater tests). Most OBD II monitors are disabled below 20°F.
 
So if the ECM is containing the intake heater then y is the dodge dealer telling me the PCM controls it
 
because they don't know much, lol...

I can tell you what pin numbers of the connector on the ECM of an 01 dodge controls each relay if you want?
 
I was thinking it was the PCM, but that might just be on the older trucks.
 
Connector A at the ECM

pin # 14 is coolant temp signal
pin # 7 IAT signal
pin # 29 Intake air heater # 1 control (ECM provides power to the relay)
pin # 47 Intake air heater # 2 control (ECM provides power to the relay)
 
Thanks guys il check to conectors on the ECM so if i replace my ECM can i just use a used one off of another auto when i replaced the ECM on my 5speed i bought a used one an it never hurt nothin jus stuck it right on i was jus wondering if it would hurt my auto or should i get the used ECM flashed before installing it
 
Maybe This wouldnt work, but could you install a push button switch, like a starter switch to warm the grid heaters from in the cab? At $10 switch is alot cheaper then a ECM.

Rick
 
ramsport59 said:
Maybe This wouldnt work, but could you install a push button switch, like a starter switch to warm the grid heaters from in the cab? At $10 switch is alot cheaper then a ECM.

Rick
Click to expand...

it would work and be cheaper than an ECM.
 
Yea i can wire it on a switch but I'd rather it work like designed but my question is now can i put a used ECM off of another auto i put a used ECM on my 5speed when the original crashed and it was fine never hurt a thing and there's quite a few used Ecm's around here i can get one for 300 jus wanna be absolutely sure that it be alight to put a used one on i don't see what it would hurt
 
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