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Home/DTC Codes/Chevrolet/Spark EV/2014-2016 Electric Motor/P1637
P1637

Generator L-Terminal Circuit

2014-2016 Chevrolet Spark EV Electric Motor

Moderate SeverityPowertrain

Description

The PCM detected a fault on the generator (alternator) L-terminal circuit. The PCM applies ignition voltage to the L-terminal to initiate generator operation. When the generator reaches operating speed, the L-terminal current stops. The PCM monitors this circuit for opens and shorts. Note: The MIL will NOT illuminate for this code (non-emissions DTC).

Symptoms

  • Battery warning light on dashboard
  • Dim or flickering headlights
  • Battery draining
  • Electrical system issues
  • Difficulty starting

Common Causes

  • Faulty generator/alternator (internal regulator)
  • Open or shorted L-terminal wiring
  • Non-OEM aftermarket alternator not communicating properly
  • Corroded connector
  • PCM failure (rare)

Diagnostic Steps

  1. Test generator output voltage and current
  2. Inspect L-terminal wiring from generator to PCM
  3. Check for proper voltage on L-terminal (low with key on/engine off, ignition voltage when running)
  4. Test with OEM alternator if aftermarket is installed
  5. Inspect connector for corrosion

Repair Notes

Test alternator output. If using aftermarket alternator, verify it communicates the 5V reference properly (OEM alternators recommended). Check L-terminal wiring.

Related Codes

P1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal CircuitP1638Generator F-Terminal Circuit

Other Powertrain Codes

P1637 on Other Vehicles

Chevrolet Astro

1995-2005 4.3L V6 Vortec

Chevrolet Avalanche

2002-2006 5.3L V8 Vortec

Chevrolet Avalanche

2002-2006 8.1L V8 Vortec

Chevrolet Avalanche

2007-2013 5.3L V8 Vortec

Chevrolet Avalanche

2007-2013 6.0L V8 Vortec

Chevrolet Aveo

2012-2018 1.6L I4

Chevrolet Beat

2018-2021 1.2L I4

Chevrolet Beretta

1990-1996 2.2L I4

Common Questions

What does code P1637 mean on a 2014-2016 Chevrolet Spark EV?

P1637 stands for "Generator L-Terminal Circuit". The PCM detected a fault on the generator (alternator) L-terminal circuit. The PCM applies ignition voltage to the L-terminal to initiate generator operation. When the generator reaches operating speed, the L-terminal current stops. The PCM monitors this circuit for opens and shorts. Note: The MIL will NOT illuminate for this code (non-emissions DTC).

What are the symptoms of P1637 on a Chevrolet Spark EV?

Common symptoms of P1637 include: Battery warning light on dashboard, Dim or flickering headlights, Battery draining, Electrical system issues, Difficulty starting.

What causes P1637 on a 2014-2016 Chevrolet Spark EV?

Common causes of P1637 include: Faulty generator/alternator (internal regulator), Open or shorted L-terminal wiring, Non-OEM aftermarket alternator not communicating properly, Corroded connector, PCM failure (rare).

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