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P1637 Chevrolet Code - Generator L-Terminal Circuit

- Code Popularity: 51,244 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P1637 Chevrolet?

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 Chevrolet?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1637 Chevrolet code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

When is the Code Detected?

When the Powertrain Control Module (PCM) detects a fault (circuit shorted to ground, or circuit shorted to a voltage), the P1637 code will set.

What are Code Possible Symptoms?

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

Code P1637 Chevrolet Description

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.

OBDII Code P1637 Chevrolet - Generator L-Terminal Circuit - AutoCodes.com
P1637 Chevrolet Code - Generator L-Terminal Circuit

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Code P1637 Chevrolet comments

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