Top Problems GMT 400 (1988-2002)

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Chevy GMC Trucks

A classic truck, the 4th generation of Chevy C/K trucks like the C1500, K1500, also known as the GMT 400 or Chevy OBS (Old body style or original body style) truck, consists of a wide range of years spanning from 1988 to 2002, and with such a large range of years has come a few common problems owners have reported. We cover the top problems of this generation like the door handles, the ABS brake system, and the fuel pump, which also applies to its sister GMC C/K trucks. Find out their symptoms, causes, and fixes with these tips from our expert mechanics.

Top Problems on the GMT 400 (1988-2002)

1. Problems with the Distributor

The distributor on 88-02 GMC and Chevrolet C1500, K1500, C2500, etc. trucks is located near the firewall. This problem outlined is for C/Ks with the Chevy 350 or 5.7L V8 engine and will be a little different for the V6 and does not apply to diesels.

Symptoms of Distributor Problems

  • Rough running engine
  • Engine stalls when driving
  • Engine doesn’t start
  • Lack of acceleration or engine feels sluggish

Causes of Distributor Problems

The wheel under the distributor cap sends a signal to the module, which sends a signal to the ignition coil. There is only one coil since 88-02 Chevy trucks do not have a coil-over-plug. The coil sends the spark to the top of the distributor cap, through the rotor which will spin and send a spark to each wire. The spark then travels to the spark plugs for combustion.

  • Sometimes the distributor wheel will crack or the distributor wheel wears out
  • Sometimes the ignition control module fails and gives no spark or an intermittent spark
  • If the acceleration feels sluggish, it could be from a clogged fuel filter

How to Fix Distributor Problems in the GMT 400

  • Keep up maintenance with the distributor cap, rotor, plug and wire replacements
  • If the engine doesn’t start, check if it has spark or fuel. If the problem is a lack of spark, inspect the parts of the distributor, and if there is no spark at the coil, there is likely a problem with the distributor or the ignition module. The ignition module can be replaced separately but the distributor tends to be inexpensive and it might be better to just replace the distributor
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2. Fuel Pump Problems

The fuel pump is located in the fuel tank and feeds pressure through the fuel lines and the fuel filter and up to the engine to the throttle body injection (TBI) system.

Symptoms of Fuel Pump Problems on the 88-02 GMT 400

  • Rough running engine
  • Stumbling engine
  • Lack of engine power
  • Truck does not start

Causes of a Bad Fuel Pump in the GMT 400

Fuel pumps tend to wear out from use.

How to Fix a Bad Fuel Pump

  • Fuel pump removal involves jacking underneath the fuel tank to support it and removing the bolts from the straps. Lower the tank to the ground to access the fuel pump.
  • Check the fuel pressure since TBI systems on some trucks will be different

3. ABS Brake Problems

ABS control module located near windshield wiper fluid reservoir on the 88-02 Chevy C/K Truck
ABS control module located near windshield wiper fluid reservoir

The ABS control module and pump on the 88-02 GMT 400 is located near the windshield wiper fluid reservoir. Brake fluid travels though the master cylinder, through the ABS control module and pump, and out to the wheels.

Symptoms of ABS Brake Problems on the 88-02 GMT 400 Truck

  • Brake fluid falls low and air gets into the system, causing low or soft brake pedal
  • Worn ABS speed sensor wiring

Causes of ABS Brake Problems

  • On these trucks air can get into the ABS system and requires bleeding the brakes to fix it
  • Sometimes the wires on the wheel speed sensors wear, for example, the protective rubber wears away from rubbing against the rotor because there is no backing shield

How to Fix ABS Problems

  • If the brake fluid ran low, air got into the system, and the brakes need to be bled, there is a special bleeding procedure that involves a scan tool.
  • There is also a manual procedure for bleeding this system that involves removing a cap from the ABS control module to get to a bleeder valve, having an assistant press on the brakes, and pressing the valve with a flat blade screwdriver or a pick. Press down on the valve and release it, then release the brake pedal and repeat for a few times.
  • If the ABS speed sensor wiring has worn, it’s not possible to replace the ABS speed sensor wiring harness so the whole sensor needs to be replaced.

4. Broken Interior and Exterior Door Handles

Symptoms of Broken Interior and Exterior Door Handles on the GMT 400

  • Components of the door handles break, making it difficult to open the truck doors from the outside or inside

How to Fix an Interior or Exterior Door Handle

  • Steps for changing an inside or outside door handle involve removing the door panel and unbolting and removing the handle

5. Broken Heater Controls

Symptoms of Broken Heater Controls

  • Heater control switches not working
  • Difficulty directing air flow
  • Buttons on the heater control panel break

How to Fix Broken Heater Controls

  • Steps involve removing the trim piece and then removing the control panel

Bonus! Tailgate Handle and Cable Problems

Symptoms of Tailgate Problems

  • Tailgate handle won’t open the tailgate
  • Tailgate won’t close and latch
  • Tailgate cables rust and break

Causes of Tailgate Problems

  • The tailgate handle rusts over time, causing the handle rods to stick and not pull the latches on each side
  • If the tailgate won’t close, it’s because the tailgate handle rods are detached and the handle will need to be replaced
  • The tailgate cables corrode from use and exposure to outdoor elements

How to Fix GMT 400 Tailgate Problems

  • Replace the tailgate handle. Steps involve unclipping the tailgate handle bezel, removing the bolts from the tailgate panel on the backside of the tailgate, disconnecting the handle rods, and replacing the tailgate handle
  • Replacing the tailgate cables include removing the bolt and detaching the cable

Replace These and Other Parts Yourself

Complete these and many more repairs on the GMT 400 truck with how-to videos in 1A Auto’s video library

Shop 4th Gen (1988-2002) Chevy and GMC C/K Truck Parts Mentioned in This Article

Related Content

4th Generation GMT 400 Model Years

  • C1500 “1/2 Ton” (1988-1999)
  • C2500 “3/4 Ton” (1988-2000)
  • C3500 “1 Ton” (1988-2002)
  • K1500 “1/2 Ton” (1988-1999)
  • K2500 “3/4 Ton” (1988-2000)
  • K3500 “1 Ton” (1988-2000)
Summary
GMT400 Problems | 4th Gen Chevy C/K Trucks (1988-2002)
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GMT400 Problems | 4th Gen Chevy C/K Trucks (1988-2002)
Description
We cover the top problems of the GMT400 pick-up truck including door handles, the ABS brake system, and the fuel pumps. Find out their symptoms, causes, and fixes with these tips from our expert mechanics.
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1A Auto
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