1992-1995 LT1 Trouble codes OBD I
Pulling codes for the is same as for the earlier TPI systems on the 1992 through 1995 F body (Camaro-Firebird). 1992-93 Corvette.
The 1994-95 Corvette was the "phase in" years for the OBD II with the 16 pin diagnostic link which requires a scanner to enable pulling codes.
1994-95 Corvette Diagnostic Link partial OBD II
Click on code number to jump down directly to description.
|13||Oxygen sensor circuit wiring/connection||55||Lean fuel monitor|
|14||Coolant sensor high temp. indicated||58||Trans Fluid high temp. indicated|
|15||Coolant sensor low temp. indicated||59||Trans Fluid low temp. indicated|
|16||Ignition low resolution pulse not detected||61||Low R134A pressure indicated|
|21||TPS signal voltage high||63||Right heated O2 sensor lean indicated|
|22||TPS signal voltage low||64||Right bank O2 sensor lean indicated|
|23||IAT sensor low temp. indicated||65||Right bank O2 sensor rich indicated|
|24||VSS fault, no pulse indicated||66||A/C pressure sensor low pressure|
|25||IAT sensor high temp. indicated.||67||A/C pressure sensor circuit fault|
|26||EVAP purge control solenoid circuit.|
|27||EGR vacuum solenoid circuit||68||A/C relay fault|
|28||Transmission range control circuit||69||A/C relay fault|
|29||Secondary air injection circuit||70||A/C high pressure indicated|
|32||EGR failure||71||A/C evap sensor low temp indicated|
|33||MAP sensor signal high||72||VSS signal circuit error|
|34||MAP sensor signal low||73||Trans. pressure solenoid current surge|
|36||Ignition faulty high resolution signal||74||Traction control system|
|37||TCC brake switch stuck ON||75||Transmission system low voltage|
|38||TCC brake switch stuck OFF||77||Cooling fan relay control|
|39||Clutch switch error||79||Trans. temp sensor high temp. indicated|
|41||No ignition control circuit||80||Trans. component harness fault|
|42||Ignition control module circuit||81||Trans 2-3 shift solenoid circuit|
|43||Knock sensor wiring open or shorted||82||Trans 1-2 shift solenoid circuit|
|44||Lean exhaust detected||83||reverse switch inhibit circuit|
|45||Rich exhaust detected||84||Skip shift or 3-2 shift solenoid circuit|
|46||VATS pass key circuit fault||85||TCC stuck ON|
|47||Knock sensor module or circuit||90||TCC solenoid circuit fault|
|91||Skip shift lamp circuit|
|48||MAF sensor circuit||97||VSS output signal voltage low|
|50||System voltage low||99||TACH output circuit|
|53||System voltage high|
Description of error codes and possible fixes
Code 13- Oxygen Sensor circuit. Check for wiring and connections problems from the O2 sensor back to the ecm. If no problem is found, replace sensor.
Code 14- Coolant sensor circuit-high temperature indicated. Verify engine is not overheating, and correct any cooling system related problems first. Check the wiring and connections to the sensor. Replace sensor.
Code 15- Coolant sensor circuit-low temperature indicated. Verify engine is not under cooling, such as a thermostat sticking open. Check wiring and connections to sensor. Replace sensor.
Code 16- Low resolution pulse (distributor). ECM is not detecting the 4X pulse from distributor. Check wiring connections, especially the pigtail connector from the optispark to main wiring harness. This is the black/red wire that goes to terminal "A" on the pigtail connector. On the 1992-93 ecm, this is wire C5 (green connector). 1994-95 ecm, this is wire B2 (black connector). If wiring checks out, you will have to replace the optical sensor module in the distributor.
Code 21- TPS sensor circuit- high voltage indicated. Check for sticking or misadjusted sensor. Check the wiring connections from sensor to the ecm. Replace sensor if wiring checks out.
Code 22- TPS sensor circuit-low voltage indicated. See code 21.
Code 23- IAT (Intake Air Temperature) sensor. Low temperature indicated. Check wiring and connections back to ecm. If wiring checks out, replace sensor.
Code 24- Vehicle Speed Sensor. This fault should happen only when vehicle is moving. Ignore code if drive wheels are not moving. Check the TPS sensor, and check the VSS connections at the sensor back to the ecm. Verify VSS sensor is faulty with a sensor tester such as a Sunspro Sensor Tester Plus-TM, before condemning sensor as faulty.
Code 25- IAT sensor. Check the resistance of the sensor and verify that it is reasonably within range based on ambient temperature. (see chart). Check wiring and connections back to ecm.
|Engine Coolant Temperature Sensor or
Manifold Air Temp Sensor (F & C)
|Resistance in Ohms|
Code 26- EVAP purge control solenoid circuit. EVAP solenoid circuit indicated as faulty. Check wiring and connections.
Code 27- EGR vacuum control solenoid circuit. Check the EGR solenoid wiring and connections.
Code 28- Transmission Range (1994-95). Check the transmission control range circuit for any opens or shorts. Verify transmission range pressure switch is working. Range "A" is on ecm pin "C28" to terminal "N" on transmission plug in, Range "B" is on ecm pin "C29" to terminal "R", Range "C" is on ecm pin "C30" to terminal "P".
Code 29- Secondary Air Injection. Check the wiring and connections for shorts.
Code 32- EGR Failure. Check for proper vacuum from source to valve. Check all vacuum hoses. Check all electrical connections from egr to ecm. Check EGR for any sticking or binding, replace if necessary. Replace ecm only if all other checks have been verified.
Code 33- MAP sensor signal voltage high. Check vacuum hoses to MAP sensor. Check wiring and connections for any shorts or opens. Replace sensor.
Code 34- MAP sensor signal low. See code 33.
Code 36- Distributor ignition system. Faulty high resolution (360X) pulse or multiple low resolution pulses detected. Check pigtail connector from distributor to main harness for any opens or shorts. Verify wiring is okay before replacing distributor.
Code 37- TCC brake switch error. stuck "ON". (1994-95) Faulty TCC brake switch, wiring or connectors. Verify 12V present at connector and when brake is not applied there is 12V power to the blue wire from the switch and when brake is applied there is no power. Verify this at the ecm Pin C14 (clear connector).
Code 38- TCC brake switch error, stuck "OFF". (1994-95). See Code 37 above.
Code 39- Clutch switch error. Fault in circuit from clutch switch to ecm. Verify connections and circuits for no shorts or opens.
Code 41- Ignition control circuit. Check pigtail harness from distributor for shorts or opens.
Code 42- Ignition control circuit (ignition module). Check wiring and connections from ignition module and ecm. Replace module only after verifying wiring and connections are not shorted or open.
Code 43- Knock sensor circuit. Check ecm for open or short to ground. Check routing of wiring, including spark plug wires near knock senor wiring, reroute as necessary. Replace knock sensor.
Code 44- Lean exhaust indicated. Check for possible lean fuel possibilities, such as low pressure caused by faulty regulator, fuel pump or fuel lines kinked or partially collapse, vacuum leaks, clogged air filter or fuel filter.. Check wiring and connections to O2 sensor. Check ground terminals to ecm. Replace O2 sensor.
Code 45- Rich exhaust indicated. Check possibilities for a rich condition, such as faulty EVAP system canister for fuel contamination, fuel in oil, leaky injectors, faulty fuel regulator or one or more leaky fuel injectors. Also check EGR system for sticky valve or faulty control circuit. Replace O2 sensor.
Code 46- VATS fault (PASS Key). Check for faulty ignition switch and/or circuit to VATS module and ecm.
Code 47- Knock sensor module. Check for faulty circuit from knock sensor or missing sensor. Replace knock sensor after verifying with a tester such as Sunspro Sensor Tester Plus-TM.
Code 48- MAF sensor circuit. Check for faulty circuit from MAF sensor to ecm. Check connections and wiring for shorts or opens.
Code 50- Charging system, low voltage indicated. Check charging system, such as caused by low alternator output, faulty field circuit, open wiring in charging system and battery condition.
Code 51- PROM/EEPROM error. Faulty or incorrect prom/eeprom. Diagnosis should be performed by authorized dealer or qualified shop.
Code 53- System overcharging. This code will set if the ecm sees more than 17 volts, or less than 10 volts. Overcharge is mostly likely the cause of a faulty voltage regulator in the alternator. Have charging system checked before replacing alternator.
Code 55- Lean fuel monitor. Engine running lean during power acceleration. Possible causes include fuel pump failure, restricted filter, restricted fuel lines, or one or more clogged injectors.
Code 58- Transmission Fluid temperature (1994-95). TFT circuit indicates high temperature. Check connections and wiring. Sensor should read between 2.9K-4K ohms at 20C.(68F).
Code 59- Transmission fluid temperature (1994-95). See code 58 above.
Code 61- Air conditioning circuit performance. Check A/C system for possible low pressure in R134A freon.
Code 63- Right bank heated O2 sensor (1994-95). Check wiring and connections to the O2 sensor, open circuit indicated. If wiring verifies ok, replace sensor.
Code 64- Right bank O2 sensor (1992-93). Lean exhaust indicated. Check wiring and connections before replacing sensor.
Code 65- Right bank O2 sensor (1992-93). Rich exhaust indicated. Check wiring and connections before replacing sensor.
Code 66- A/C pressure sensor circuit. Check sensor connector and wiring for opens or shorts. Replace pressure sensor.
Code 67- A/C freon pressure sensor circuit. Check pressure sensor and/or A/C clutch for possible short to ground. Replace pressure sensor.
Code 68- A/C relay circuit fault. Check relay circuit for open or ground condition. Repair as necessary. Replace relay.
Code 69- A/C relay circuit fault. Check relay circuit for open or ground condition. Repair as necessary. Replace relay.
Code 70- A/C pressure sensor-high pressure indicated. Check pressure sensor and/or A/C clutch for possible short to ground or open circuit in sensor wiring. Replace sensor after verifying wiring and connections are okay.
Code 71- A/C evaporator temperature sensor. Low temperature indicated. Check pressure sensor and/or A/C clutch for possible short to ground or open circuit in sensor wiring. Replace sensor after verifying wiring and connections are okay.
Code 72- VSS signal circuit error. Check the VSS and circuit for short to ground or open circuit, a bare wire can cause an intermittent problem. Verify this first. Also check the VSS to make sure no excessive material has built up on the magnetic end, such material from the transmission wearing over a period of time cause deposit fine shavings on sensor head interfering with sensor operation. Wipe clean with paper (not cloth) towel to remove material and reinstall. A newly rebuilt transmission can deposit these quick enough as the transmission is "breaking in". If all else checks out, replace sensor.
Code 73- Pressure control solenoid. (1994-95). Check the pressure solenoid. Normal resistance is between 3-8 ohms at 20C (68F).Replace if out of range. Check lines for damage. Check for clogged filter and replace f necessary.
Code 74- Traction control system (1994-95 F & Y body). Low voltage indicated in traction control circuit. Check for shorted to ground or open circuit.
Code 75- Transmission system-low voltage indicated. Pressure control solenoid possible malfunction. Normal resistance is between 3-8 ohms at 20C (68F). Check ignition power feed to ecm for intermittent or direct open.
Code 77- Cooling fan control relay circuit. Check relay circuit for open or shorts to ground. If no wiring problems are found, replace relay. Be careful as intermittent short or open can only be detected by wiggling the wires and observing any voltage fluctuations to the affected circuit.
Code 79- Transmission Fluid temperature (1994-95 F&Y body). TFT sensor defective or excessive heat in transmission. Check for overheated condition first, low fluid level, faulty TCC lock up or excessive low gear operation.
Code 80- Transmission component harness failure. Possible TCC problem. Transmission slipping due to excessive heat or low fluid level.
Code 81- Transmission 2-3 shift solenoid circuit (1994-95 F&Y body). 2-3 solenoid circuit or solenoid fault. Check solenoid for proper resistance, should read between 20-40 ohms at 20C (68F).
Code 82- Transmission 1-2 shift solenoid circuit (1994-95 F&Y body). 1-2 solenoid circuit or solenoid fault. Check solenoid for proper resistance, should read between 20-40 ohms at 20C (68F).
Code 83- Reverse inhibit system (manual transmission). Vehicle must be under 4 mph to allow reverse operation.
Code 84- Skip shift solenoid circuit fault. (manual transmission 1994-95 F&Y body). Check wiring and connections for opens or shorts. Check solenoid for open or shorted condition.
3-2 shift control circuit (automatic trans. 1994-95 F&Y body). Check wiring and connections for opens or shorts. Check solenoid for proper resistance of 9-14 ohms at 20C (68F).
Code 85- Transmission TCC stuck "ON". TCC stuck on, check the wiring and connections. TCC solenoid pressure port possibly clogged causing TCC to stay locked up, meaning pan will have to be pulled to correct. Check solenoid for proper resistance of 20-40 ohms.
Code 90- Transmission TCC solenoid fault. Check TCC circuit for opens or grounds, check solenoid resistance. (see above).
Code 91- Skip shift lamp defective. manual transmission 1994-95 F&Y body). Check wiring for shorts or open to ecm pin D15 (blue connector).
Code 97- VSS low voltage indicated. Check VSS and circuit for opens or grounds. See Code 72.
Code 99- TACH output circuit (1994-95 F&Y body). Check for loose, damaged, or shorted tach output wire from coil. This is the whit wire on the black connector that goes to the ignition coil. If all checks out as far as wiring, and code is still present you will need to take it to dealer or authorized service repair center.
ECM schematics: (1992-93 Y Body, 1993 F body) (1994-95 B, F and Y body)