What Does P1356 Mean?
The Powertrain Control Module (PCM) has lost communication with the Ignition Diagnostic Module (IDM). This indicates a breakdown in the data signal between these two critical control modules that coordinate spark timing and delivery.
Safety Warning
Engine may not start or can stall unexpectedly during operation, creating dangerous driving conditions. Vehicle should not be driven until repaired.
Common Causes
35%
Damaged or corroded wiring harness between IDM and PCM
30%
Failed Ignition Diagnostic Module (IDM)
20%
Poor ground connection at IDM or PCM
15%
Failed PCM internal circuitry
Diagnostic Steps
1
Step 1: Visually inspect IDM and PCM connectors for corrosion, bent pins, or damage
2
Step 2: Check voltage supply to IDM module (typically 12V ignition feed)
3
Step 3: Verify ground circuit integrity at both IDM and PCM with voltage drop test
4
Step 4: Test communication signal wire between IDM and PCM for continuity and resistance
5
Step 5: Substitute known-good IDM if available to isolate module failure
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
The Powertrain Control Module (PCM) has lost communication with the Ignition Diagnostic Module (IDM). This indicates a breakdown in the data signal between these two critical control modules that coordinate spark timing and delivery.
The most common cause of P1356 (Loss of Ignition Diagnostic Module Input to PCM) is: Damaged or corroded wiring harness between IDM and PCM
Typical repair costs for P1356 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Engine may not start or can stall unexpectedly during operation, creating dangerous driving conditions. Vehicle should not be driven until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1356 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition System
Difficulty
Type
Manufacturer
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