HOW TO DIAGNOSE ISUZU OBD1 WITHOUT OBD SCANNER FROM YEAR 1991-1999
Preparatory conditions
Ensure battery voltage above 11 volts.
Transmission in neutral.
All auxiliary equipment, including air conditioning, switched OFF.
Method 1 – except Germany
- Trouble codes are displayed by the malfunction indicator lamp (MIL).FIG3
- Switch ignition ON.
- Check that MIL illuminates.
- Install a spare fuse to diagnosis socket in fusebox Fig. 1 [1].
- Count MIL flashes. Note trouble codes. Compare with trouble code table.
- Each trouble code consists of two groups of one or more flashes.FIG.2
- A 1,5 second pause separates each trouble code group.
- A 3 second pause separates each trouble code.
- MIL flash duration: 0,3 second.
- For example: Two 0,3 second flashes – 1,5 second pause – one 0,3 second flash. Trouble code 21.
- Remove fuse.
- Switch ignition OFF.
Method 2 – Germany
- Trouble codes are displayed by the malfunction indicator lamp (MIL).FIG3
- Switch ignition ON.
- Check that MIL illuminates.
- Install a spare fuse to diagnosis socket in fusebox Fig. 1 [1].
- Bridge diagnosis connector terminals Fig. 1 [2].
- Count MIL flashes. Note trouble codes. Compare with trouble code table.
- Each trouble code consists of two groups of one or more flashes.FIG2
- A 1,5 second pause separates each trouble code group.
- A 3 second pause separates each trouble code.
- MIL flash duration: 0,3 second.
- For example: Two 0,3 second flashes – 1,5 second pause – one 0,3 second flash. Trouble code 21.
- Remove fuse. Remove bridge wire.
- Switch ignition OFF.
Erasing trouble codes
- Ensure ignition switched OFF.
- Disconnect battery earth lead for 20 seconds minimum.
- Reconnect battery earth lead.
- Repeat checking procedure to ensure no data remains in ECM fault memory.
WARNING: Disconnecting the battery may erase memory from electronic units (e.g. radio, clock).
OBD1 CODES
Trouble code | Fault location | Probable cause |
| 12 | No fault found | – |
| 13 | Heated oxygen sensor (HO2S) – circuit malfunction | Wiring, HO2S, ECM |
| 14 | Engine coolant temperature (ECT) sensor – circuit malfunction | Wiring, ECT sensor, ECM |
| 15 | Engine coolant temperature (ECT) sensor – signal malfunction | Wiring, ECT sensor, ECM |
| 21 | Throttle position (TP) sensor – signal voltage high | Wiring, TP sensor, ECM |
| 22 | Throttle position (TP) sensor – signal voltage low | Wiring, TP sensor, ECM |
| 23 | Intake air temperature (IAT) sensor – circuit malfunction/intermittent voltage high | Wiring, IAT sensor, ECM |
| 24 | Vehicle speed sensor (VSS) – signal malfunction | Wiring, VSS, ECM |
| 25 | Intake air temperature (IAT) sensor – circuit malfunction/intermittent voltage low | Wiring, IAT sensor, ECM |
| 31 | Manifold absolute pressure (MAP) sensor – signal voltage low | Wiring, MAP sensor, ECM |
| 32 | Manifold absolute pressure (MAP) sensor – signal voltage high | Wiring, MAP sensor, ECM |
| 33 | Mass air flow (MAF) sensor – signal voltage high | Wiring, MAF sensor, ECM |
| 34 | Mass air flow (MAF) sensor – signal voltage low | Wiring, MAF sensor, ECM |
| 41 | Ignition fail safe signal – circuit malfunction | Wiring, noise suppressor, ignition control module (ICM), ECM |
| 42 | Crankshaft position (CKP) sensor/camshaft position (CMP) sensor – signal malfunction | Wiring, CKP/CMP sensor, ECM |
| 44 | Closed throttle position (CTP) switch – signal malfunction | Wiring, CTP switch, ECM |
| 45 | Closed throttle position (CTP) switch – signal malfunction | Wiring, CTP switch, ECM |
| 51 | Exhaust gas recirculation (EGR) solenoid – circuit malfunction | Wiring, EGR solenoid, ECM |
| 52 | Injector leak/heated oxygen sensor (HO2S) – circuit malfunction | Wiring, injector/HO2S, ECM |
| Light remains ON | Engine control module (ECM) | ECM |