Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

SYS.OK|MANUAL.DB● LIVE

HOMESERVICE MANUALSCHEVROLET1993SUBURBAN C2500, 5.7 KREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - TRANSMISSIONSELF-DIAGNOSTIC SYSTEMTROUBLE CODE IDENTIFICATION

1993 Chevrolet Suburban C2500, 5.7 K

Trouble Code Identification

1993 Chevrolet Suburban C2500, 5.7 KSECTION Trouble Code Identification

NOTE: Trouble codes retrieved from PCM/TCM may be related to either engine or transmission. Transmission-related codes are covered in this article. For engine-related codes, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. See TROUBLE CODE IDENTIFICATION table to determine if code is transmission or engine related.

The system codes indicate failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of the control module. Code 51 indicates PROM/MEM-CAL is installed improperly or has failed.
Code 55 indicates PCM/TCM has failed (except on 3.8L) and must be replaced. If the condition is still not corrected after replacing PCM/TCM, the cause may be as follows.
- An incorrect PCM/TCM or PROM/MEM-CAL application may cause a malfunction, which may or may not set a code.
- The PCM/TCM connector may be the problem. Connector terminals may have to be removed from the connector to be properly checked.
- PROM/MEM-CAL failure. Although the PROM/MEM-CAL rarely fails, it could be the cause of the problem.
- Replacement PCM/TCM may be faulty.
- Intermittent problem. Make a careful physical inspection of affected sensor/circuit.
- A shorted solenoid, relay, or harness may be the cause of PCM/TCM failure. Use Short Circuit Tester (J-34636) to check for short circuits.

TROUBLE CODE IDENTIFICATION

Code

Probable Cause

⁽¹⁾ No Engine Speed Sensor Reference Pulse To PCM/TCM

⁽¹⁾ Open Oxygen Sensor Circuit

⁽¹⁾ CTS Voltage Low (Sensor Or Signal Line Grounded)

⁽¹⁾ CTS Voltage High (Sensor Or Signal Line Open)

⁽¹⁾ System Voltage High/Low (3.8L) ⁽²⁾ Transmission Speed Error

⁽¹⁾ RPM Signal Problem (3.8L)

⁽¹⁾ Cam/Crank Error (3.8L)

⁽¹⁾ TPS Voltage High (Open Circuit Or Misadjusted TPS)

⁽¹⁾ TPS Voltage Low (Circuit Grounded)

⁽¹⁾ Intake Air Temperature Sensor Voltage High

⁽³⁾ Vehicle Speed Sensor Circuit Open Or Grounded

⁽¹⁾ Intake Air Temperature Sensor Voltage Low

⁽¹⁾ Quad-Driver "A" Fault (3.8L) Quad-Driver 1 Fault (4.3L M/T "S" & "T" Pickup)

⁽¹⁾ Quad-Driver 2 Fault (4.3L M/T "S" & "T" Pickup)

⁽⁴⁾ Pressure Switch Manifold Fault

⁽¹⁾ Park/Neutral Switch Circuit (3.8L)

⁽¹⁾ Turbocharger Wastegate Overboost (4.3L Turbo)

⁽¹⁾ Engine Speed Control Governor (5.7L "G" Van)

⁽⁵⁾ MAP Voltage Low (Diesel)

⁽¹⁾ Turbocharger Wastegate Overboost (4.3L Turbo)

⁽¹⁾ EGR Error (Improper Vacuum Signal)

⁽¹⁾ MAP Voltage High (Circuit Open Or Short To Voltage)

⁽¹⁾ MAP Voltage Low (Circuit Open Or Short To Ground)

⁽¹⁾ MAF Sensor Signal Voltage Low (3.8L)

⁽¹⁾ IAC System Fault

⁽¹⁾ Shift Control Problem (3.8L)

⁽⁴⁾ Brake Switch Stuck On (4L60-E)

⁽¹⁾ Brake Switch Circuit (3.8L) Knock Sensor Circuit Open (4.3L M/T "S" & "T" Pickup) ⁽⁴⁾ Brake Switch Stuck Off (4L60-E)

TCC Stuck Off (⁽¹⁾ 3.8L & ⁽⁴⁾ 4L80-E)

⁽¹⁾ Knock Sensor Circuit Shorted (4.3L M/T "S" & "T" Pickup)

⁽¹⁾ Cam Sensor Circuit (3.8L)

⁽¹⁾ EST Circuit Fault

⁽¹⁾ ESC Fault

⁽¹⁾ Lean Exhaust Indicated

⁽¹⁾ Rich Exhaust Indicated

⁽¹⁾ Improperly Installed/Faulty PROM/MEM-CAL

⁽⁴⁾ Long System Voltage High (4L60-E) ⁽¹⁾ Fuel CALPAC Missing

⁽³⁾ System Voltage High (Charging System Problem)

53, 54 & 55

⁽¹⁾ EGR Fault (3.8L)

⁽¹⁾ Fuel Pump Circuit Voltage Low

⁽¹⁾ Faulty ECM/PCM

⁽¹⁾ Quad-Driver "B" Fault (3.8L)

⁽⁴⁾ TTS High Temperature (Sensor Or Signal Line Grounded)

⁽⁴⁾ TTS Low Temperature (Sensor, Connections Or Wires Open)

⁽¹⁾ Cruise Vent Solenoid (3.8L)

⁽¹⁾ Cruise Vacuum Solenoid (3.8L)

⁽¹⁾ Cruise System Problem (3.8L)

⁽¹⁾ Cruise Servo Position (3.8L)

⁽¹⁾ Low A/C Refrigerant Charge (3.8L)

⁽⁴⁾ 3-2 Control Solenoid Fault (4L60-E)

⁽⁴⁾ TCC Solenoid Circuit Fault (4L60-E) ⁽¹⁾ Cruise Engage Switches (3.8L)

⁽⁴⁾ Overdrive Ratio Error

(Engine RPM Greater Than Input Speed)

⁽¹⁾ Cruise System Problem (3.8L)

⁽⁴⁾ Torque Converter Stuck On (4L60-E) ⁽¹⁾ A/C Head Pressure Switch (3.8L)

⁽⁴⁾ VSS Signal Loss (4L60-E)

⁽⁴⁾ Force Motor (Pressure Control Solenoid) Error

⁽⁴⁾ System Voltage Low (Charging System Problem)

⁽⁴⁾ Transmission Fluid Temperature High (4L60-E)

⁽⁴⁾ Solenoid "B" (2nd-3rd) Circuit Fault

⁽⁴⁾ Solenoid "A" (1st-2nd) Circuit Fault

⁽⁴⁾ TCC Solenoid Circuit Fault (4L80-E)

⁽⁴⁾ Undefined Gear Ratio (4L80-E)

⁽⁴⁾ Low Gear Ratio (4L80-E)

⁽⁴⁾ High Gear Ratio (4L80-E)

⁽¹⁾	Gasoline engine code. See appropriate TESTS W/CODES article in this section.

⁽²⁾	Models equipped with 4L60-E transmission, and 4.3L "S" and "T" series utility vehicles with man. trans.

⁽³⁾	Common gasoline engine and transmission code. See appropriate TESTS W/CODES article in this section.

⁽⁴⁾	Transmission code. Covered in this article.

⁽⁵⁾	Diesel engine code. For diesel code diagnosis, see G - DIESEL TESTS W/ CODES article in this section.

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready Tools Free Quote Check Quote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.