Case IH 3270 – Engine Control Unit (ECU / ECM) / EDC: Grid Heater Switch On Test - Voltage Drop Too Low

During the engine's automated cold-start diagnostic test, the control module commands the intake grid heater to turn on. The system monitors the electrical circuit for a specific voltage drop to confirm the heater is drawing the massive amount of current it requires to warm the intake air. A 'Voltage Drop Too Low' indicates that the heater is not drawing the expected current. This is almost always caused by an open circuit—such as a burnt-out grid heater element, a failed grid heater relay that isn't closing, a blown high-amp fuse/fusible link, or a broken/disconnected heavy-gauge cable.

• Magnum 235 - 340 (Series 4)
• Steiger series
• Puma series (145, 175, 185 CVT)
• Patriot 3230
• T8.xxx Series
• T6 Series

1. 1

   Check the high-amp fuses or circuit breakers (often 300A) supplying power from the battery to the grid heater relay.

2. 2

   Inspect heavy-gauge wiring from the battery to the relay, and from the relay to the grid heater element for loose retaining nuts, severe corrosion, or broken cables.

3. 3

   Test the grid heater relay by listening/feeling for a click when the key is turned on during a cold start, and test for voltage exiting the relay toward the heater when commanded on.

4. 4

   Ohm-test the grid heater element by disconnecting the power cable at the heater and measuring resistance to ground. An 'OL' (open line) reading indicates the element is burnt out.

1. 1

   Disconnect Power

   Disconnect the negative battery cable(s).

2. 2

   Access the Components

   Locate the grid heater relay (usually mounted near the engine frame bracket or firewall) and the grid heater element (bolted into the intake manifold air horn).

3. 3

   Replace Faulty Wiring (If Applicable)

   If the diagnostic checks revealed a burnt cable, unbolt the damaged cable from the relay and heater/battery terminals and install a new one.

4. 4

   Replace the Relay (If Applicable)

   If the relay failed the voltage pass-through test, detach the electrical connector for the relay coil, unbolt the heavy battery and heater cables, and unbolt the relay from its mounting bracket. Install the new relay and torque the cable nuts to specification.

5. 5

   Replace the Grid Heater Element (If Applicable)

   If the heater element is open, remove the intake piping/hoses connected to the intake horn. Unbolt the grid heater module from the intake manifold. Clean the mating surfaces, install the new grid heater with new gaskets, and reassemble the intake piping.

6. 6

   Reassemble and Clear Codes

   Reconnect the battery. Turn the key to the ON position to allow the ECM to run the Grid Heater Switch On Test. Verify that the voltage drop is now within range and clear the 3270 fault code using a diagnostic tool.