Case IH 19196 – ECM: Signal range check: low error when heater is Off

The system detects a Diagnostic Fault Check (DFC) to Signal Range Check (SRC) Low error on the intake air heater (grid heater) circuit while the heater is commanded OFF. This typically indicates a short to ground, a stuck relay, or a wiring issue causing an unexpected low voltage reading on the power stage of the air heater circuit.

• Tier 4b
• Puma series
• Puma 185 CVT
• Maxxum
• JX series
• JX55
• JX100U
• N-Series Tractor Loader Backhoes (TLBs)
• N-Series loaders

1. 1

   Battery Voltage Check: Verify that the system has proper battery voltage, as powerstage diagnosis can be affected by abnormally high or low battery voltage.

2. 2

   Relay Inspection: Test the grid heater power relay. A common failure point on these engines is the grid heater relay sticking closed, which causes a continuous battery draw or circuit error.

3. 3

   Wiring Harness Check: Inspect the grid heater wire harness and relay harness for chafing, melting, or a short circuit to ground.

4. 4

   Heater Element Check: Test the intake manifold air heater element for proper resistance and ensure the terminal posts are not shorting against the intake manifold housing.

1. 1

   Disconnect Power

   Disconnect the negative battery cables to prevent accidental shorts or electrical arcing during the repair.

2. 2

   Locate Components

   Locate the grid heater relay (often mounted near the battery or engine fuse block) and the intake air heater element on the intake manifold.

3. 3

   Remove Faulty Component

   If the relay is stuck closed or failed, unbolt the power cables and remove the relay. If the grid heater element is faulty, remove the intake air horn/cover and extract the heater element.

4. 4

   Install New Parts

   Install the replacement relay or heater element. Crucial Step: When reconnecting the grid heater power cables, ensure that all insulating washers are properly oriented. Failure to install the insulators correctly will cause a dead short to the manifold housing.

5. 5

   Reassemble

   Reinstall any removed intake manifold gaskets or covers. Reconnect the battery terminals.

6. 6

   Clear Codes

   Use the Case IH Electronic Service Tool (EST) to clear the fault code from the ECM, or cycle the ignition to verify the code does not return upon a cold start.