What Does P1398 Mean?
The ECM has detected abnormally low voltage or current in the glow plug circuit for bank #2 (the cylinder bank opposite #1). This indicates a problem with the glow plug power supply, wiring, relay, or the glow plugs themselves on that bank.
Common Causes
35%
Failed glow plug relay or control module
30%
Open circuit or damaged wiring in glow plug harness for bank 2
20%
Multiple failed glow plugs on bank 2
10%
Blown fuse or fusible link in glow plug power circuit
5%
Poor ground connection for glow plug circuit
Diagnostic Steps
1
Step 1: Inspect glow plug fuse and relay operation with a test light or multimeter
2
Step 2: Check voltage and current draw at glow plug harness connector for bank 2 during glow plug cycle
3
Step 3: Test individual glow plug resistance on bank 2 cylinders (typically 0.5-2.0 ohms when cold)
4
Step 4: Inspect wiring harness and connectors for corrosion, breaks, or damage between relay and glow plugs
5
Step 5: Check glow plug control module operation and ground circuits with bidirectional scan tool commands
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The ECM has detected abnormally low voltage or current in the glow plug circuit for bank #2 (the cylinder bank opposite #1). This indicates a problem with the glow plug power supply, wiring, relay, or the glow plugs themselves on that bank.
The most common cause of P1398 (Glow Plug Circuit Low Input (Bank #2)) is: Failed glow plug relay or control module
Typical repair costs for P1398 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains safe to drive but will experience hard starting in cold weather. Extended cranking can damage starter motor and drain battery.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1398 to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Cold Start System
Difficulty
Type
Manufacturer
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