Engine-Codes - Generic - P1637

P1637 Code - Generator L-Terminal Circuit

- Code Popularity: 33,734 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents
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What are the Possible Causes of the DTC P1637?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Generator (Alternator)
  • Generator harness is open or shorted
  • Generator circuit poor electrical connection
  • Powertrain Control Module (PCM) programming
  • Faulty Powertrain Control Module (PCM)
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How to Fix the DTC P1637?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P1637 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P1637 Code Mean?

The L-terminal circuit from the generator is a discrete circuit (a discrete circuit has no splices and only one source and one destination) into the Powertrain Control Module (PCM). The PCM applies ignition voltage to the generator L terminal circuit. A small amount of current flows from this circuit through the generator windings to create a magnetic field which starts the generator process. When the generator is at operating speed and producing voltage, a solid state switch for the L terminal circuit in the generator opens and the PCM detects that the initial startup current flow has stopped.
The PCM expects to detect low voltage on the L terminal circuit prior to the generator rotating at operating speed and conversely expects the circuit to be at ignition voltage potential when the generator is operational.

P1637 Code - Generator L-Terminal Circuit

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Code P1637 Information for Specific Makes

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