| 92-95 4.3, 5.0, 5.7, 7.4L VIN Z, H, K, N |
|---|
| Flash Code | Fault Location | Probable Cause |
| 12 | Start of diagnosis | No engine speed (RPM) signal received |
| 13 | Oxygen sensor (O2S)/heated oxygen sensor (HO2S) | Wiring open circuit, O2S/HO2S, ECM |
| 14 | Engine coolant temperature (ECT) sensor – high temperature indicated | Wiring short circuit to ground, ECT sensor, ECM |
| 15 | Engine coolant temperature (ECT) sensor – low temperature indicated | Wiring open circuit, ECT sensor, ECM |
| 16 | Vehicle speed sensor (VSS) buffer – signal low | Wiring, VSS buffer, ECM |
| 17 | Camshaft position (CMP) sensor – circuit malfunction | Wiring, CMP sensor, mechanical fault, ECM |
| 21 | Throttle position (TP) sensor – voltage high | Wiring open circuit/short circuit to positive, TP sensor, ECM |
| 22 | Throttle position (TP) sensor – voltage low | Wiring open circuit/short circuit to ground, TP sensor, ECM |
| 23 | Intake air temperature (IAT) sensor – low temperature | Wiring open circuit, IAT sensor, ECM |
| 24 | Vehicle speed sensor (VSS) | Wiring open circuit/short circuit to ground, PROM, VSS, ECM |
| 25 | Intake air temperature (IAT) sensor – high temperature | Wiring short circuit to ground, IAT sensor, ECM |
| 28 | Transmission range (TR) switch | Wiring open circuit/short circuit to ground/short circuit to positive, TR switch, ECM |
| 31 | Engine speed control system – malfunction | Wiring, throttle valve motor, throttle valve control module, ECM |
| 32 | Exhaust gas recirculation (EGR) solenoid | Wiring open circuit/short circuit to ground, EGR valve, ECM |
| 33 | Manifold absolute pressure (MAP) sensor – circuit malfunction | Wiring open circuit/short circuit to positive, hose blocked/leaking, MAP sensor, ECM |
| 34 | Manifold absolute pressure (MAP) sensor – circuit malfunction | Wiring open circuit/short circuit to ground, MAP sensor, ECM |
| 35 | Idle air control (IAC) valve | Wiring, IAC valve, intake system leaking, fuel system, PCV valve, A/C system, mechanical fault, ECM |
| 36 | Auxiliary idle air control valve | Wiring, idle air control valve, vacuum pipes, ECM |
| 37 | Brake pedal position (BPP) switch for torque converter clutch (TCC) | Wiring open circuit/short circuit to ground, incorrectly adjusted BPP switch, BPP switch, ECM |
| 38 | Brake pedal position (BPP) switch/ torque converter clutch (TCC) | Wiring open circuit/short circuit to ground, supply wire, BPP switch, TCC switch, ECM |
| 39 | Brake pedal position (BPP) switch – stuck OFF | Wiring, BPP switch, ECM |
| 42 | Ignition control module (ICM) – electronic spark timing (EST)/ignition control (IC)/bypass circuit malfunction | Wiring open circuit/short circuit to ground, ICM, ECM |
| 43 | Knock sensor (KS) | Wiring open circuit/short circuit to ground/short to positive, KS, PROM, ECM |
| 44 | Oxygen sensor (O2S)/heated oxygen sensor (HO2S) – mixture lean | Wiring short circuit to ground, fuel pressure low, MAP sensor, misfire, fuel contamination, exhaust system leaking, O2S/HO2S, ECM |
| 45 | Oxygen sensor (O2S)/heated oxygen sensor (HO2S) – mixture rich | Fuel pressure high, injector(s) leaking, O2S contamination, EVAP canister purge valve, TP sensor, MAP sensor, EGR system, O2S/H2OS, ECM |
| 46 | Immobilizer system, code – malfunction | Incorrect key, ECM |
| 51 | Engine control module (ECM) – PROM | Insecure PROM, incorrect PROM, ECM |
| 52 | Engine control module (ECM) – malfunction | ECM |
| 52 (1994-1995) | System Voltage – high | Alternator, jump started |
| 53 | System Voltage – high | Alternator |
| 54 | Fuel pump circuit – voltage low | Wiring open circuit/short circuit to ground, fuel pump relay, fuel pump, engine oil pressure warning lamp switch, ECM |
| 55 | Engine control module (ECM) | Ground wiring open circuit, insecure PROM, ECM |
| 58 | Transmission fluid temperature (TFT) sensor – voltage low | Wiring short circuit to ground, TFT sensor, ECM |
| 59 | Transmission fluid temperature (TFT) sensor -voltage high | Wiring open circuit, TFT sensor, ECM |
| 61 | Oxygen sensor (O2S) | O2S |
| 62 | Transmission gear switch signal circuit | Wiring open circuit/short circuit to ground, 2nd gear switch, 3rd gear switch, ECM |
| 68 | Torque converter clutch (TCC) – slipping | Wiring, TCC solenoid, transmission mechanical fault, ECM |
| 69 | Torque converter clutch (TCC) solenoid – stuck ON | Wiring open circuit/short circuit to ground, transmission internal wiring, TCC solenoid, transmission mechanical fault, ECM |
| 70 | A/C refrigerant pressure sensor – voltage high | Wiring open circuit/short circuit to positive, A/C refrigerant pressure sensor, ECM |
| 72 | Vehicle Speed Sensor (VSS) | Wiring open circuit/short circuit to ground, VSS, ECM |
| 73 | Transmission fluid pressure (TFP) control solenoid – circuit malfunction | Wiring, poor connection, TFP solenoid |
| 74 | Transmission input shaft speed sensor – circuit malfunction | Wiring, input shaft speed sensor, ECM |
| 75 | Exhaust gas recirculation (EGR) solenoid 1 – circuit malfunction | Wiring, EGR valve, ECM |
| 75 (1994-1995) | System voltage, engine control module (ECM) – low | Wiring, battery, alternator, ECM |
| 76 | Exhaust gas recirculation (EGR) valve solenoid 2 | Wiring open circuit/short circuit to ground, supply wire, EGR valve, ECM |
| 77 | Exhaust gas recirculation (EGR) valve solenoid 3 | Wiring open circuit/short circuit to ground, supply wire, EGR valve, ECM |
| 79 | Transmission fluid temperature (TFT) – high | Transmission mechanical fault, towing |
| 80 | Torque converter clutch (TCC) – slipping | Wiring open circuit/short circuit to ground, supply wire, transmission internal wiring, TCC solenoid, transmission mechanical fault, ECM |
| 81 | Transmission shift solenoid (SS), 2nd-3rd – circuit malfunction | Wiring, SS, ECM |
| 82 (1994-1995) | Transmission shift solenoid (SS), 1st-2nd – circuit malfunction | Wiring, SS, ECM |
| 83 | Torque converter clutch (TCC) solenoid, pulse width modulated – circuit malfunction | Wiring, TCC solenoid, ECUM |
| 85 (1994-1995) | Transmission input/output shaft speed, ratio variation – out of range | Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault |
| 86 (1994-1995) | Transmission input/output shaft speed, ratio variation – lower than expected | Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault |
| 87 (1994-1995) | Transmission input/output shaft speed, ratio variation – out of range | Wiring, input shaft speed sensor, output shaft speed sensor, mechanical fault |
| 90 | Torque converter clutch (TCC) – stuck ON | Wiring open circuit/short circuit to ground, transmission internal wiring, TCC solenoid, transmission mechanical fault, ECM |
| 96 | Engine control module (ECM) – ignition supply voltage low | Wiring open circuit, alternator, ECM |
| 98 | Engine control module (ECM) – incorrectly coded | ECM incorrectly coded, ECM |
| 99 | Engine control module (ECM) – incorrectly coded | ECM incorrectly coded, ECM |
1993 Chevy blazer 1500 have fuel but no spark. Distributor cap and rotor replaced, plugs and wires, ignition coil and ignition cylinder all new within a year. And thoughts would be appreciated
Travis,
I assumed you had a V8 in this truck. Should be the same for a V6.
Try this first.
Verify good power to the coil on the Pink wire while cranking.
Use a test light connected to the battery positive and touch the negative coil lead (White wire or Brown wire) when cranking the test light should blink. If it does, replace the coil.
If the test light does not blink while cranking, check the wire is good from the coil to the module. If it is, check ac voltage output from the pick-up coil to the module cranking with the pick-up coil disconnected from the back of the module. It should produce at least 0.7 volts ac. If less, replace the pick-up coil and if worn, the distributor shaft too.
If all this checks out, replace the ignition module.
Hope this helps.
Hey I don’t have a initial check code just flashes when checking
95 GMC 2500 diesel manual trans. check engine light comes on at 60 MPH. goes off if let up on throttle. comes back on soon. code is 78 not shown on code list. Previous code 72 speed sensor. Replaced sensor and no change. any suggestions/
Jim,
That’s the code for the Wastegate solenoid fault. You can always try a wastegate solenoid to see but it would be best to diagnose the issue.
Also, there is a TSB for a revised flowchart to diagnose.
The TSB is #61-65-19A. Check it out and go thru the diagnosis.
If you still have issues please check with a tech that’s used to working on the older 6.5L engines in GM trucks.
Good luck with this issue Jim.
BTW – the chart you referred to is for gas engines only. That’s why no code 78 in the chart.
I have a 1994 K1500 with 5.7 engine. When I check the codes I get a 67, 81, and 82. On the chart above there is no 67. I goes from 62 to 68,69, which are also for the “Wiring, TCC solenoid, transmission mechanical fault, ECM”. 81 and 82 is ” Wiring, SS, ECM”. On the previous chart on the other page it did show a 67 and said, “Wiring, SS, ECM”. I have had the ECM replaced in the last year, and the electronic ignition module replaced a couple of months ago. Right after that was changed the tach began erratically jumping about 4-500 RPMs. It doesn’t seem to me that that would be related to this. For some time now, the torque converter seems to unlock at around 40-45 RPMs, then not relock. Any suggestions how to proceed?
Hello. Does the engine overheat? This can be about 2 or 3 things. Is the engine misfiring? The strong gas smell can mean that the intake gaskets are leaking, or the fuel filter could need changed. Or an injector may be bad.The other thing it may be. The most likely thing, is a blown head gasket. Look for any misfiring code, if so, It’s pretty safe to say it has a blown head gasket.
engine dies when temp is at 210 and idles under 500 rpms, check engine light come on, does start up again and some white smoke from exhaust and strong gas smell. what could cause this?