Quick answer
The 1KZ-TE in the Hilux Surf (KZN130 and KZN185) uses Toyota's pre-OBD-II flash-code diagnostic system, not the OBD2 standard fitted to modern vehicles. You read codes by bridging two terminals on the diagnostic connector and counting the flashes of the ECT (engine check) warning light on the dash. No scan tool required. The common codes you'll actually meet in the field are 22 (water temperature sensor), 24 (intake air temperature), 31 (boost pressure / MAP), 32 (TPS), 34 (turbo pressure), 42 (vehicle speed sensor), and 51 (idle switch / neutral switch condition). A persistent Check Engine light on a healthy engine is almost always one of these sensors, not the engine itself.
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How to read 1KZ-TE diagnostic codes (no scan tool)
The 1KZ-TE pre-dates OBD-II. You can't plug a generic OBD2 scanner into a KZN130 or KZN185 and read codes. The factory diagnostic method is a manual flash-code procedure:
- Locate the diagnostic connector, usually under the bonnet near the driver's side strut tower, in a small black box labelled "Diagnostic" with a removable lid.
- Bridge terminals TC and CG with a jumper wire or paperclip. ("TE1" and "E1" on earlier connectors.) Both are on the same connector.
- Turn the ignition to ON (do not start the engine).
- Watch the Check Engine light on the dash. It will flash a coded sequence.
Each code is two digits, read in groups of pulses separated by a 1.5-second gap. For example, "two flashes, pause, two flashes" = code 22. A 4.5-second gap separates one full code from the next. "Code 1" steady-flashing means no faults stored.
To clear codes after a repair, pull the EFI fuse (15A in the engine bay fuse box) for 30 seconds, or disconnect the battery negative terminal for 30 seconds.
1KZ-TE diagnostic code reference
| Code | Meaning | Likely cause | First-pass fix |
|---|---|---|---|
| 1 | Normal, no faults stored | n/a | n/a |
| 12 | RPM signal, no signal from crank position sensor | CKP sensor wiring, sensor failure | Check CKP plug + wiring; replace sensor if signal absent |
| 13 | RPM signal, above 1000 rpm with no input | Same as code 12 at higher rpm | Same as code 12 |
| 14 | Ignition signal (petrol, doesn't apply on diesel) | n/a on 1KZ-TE | n/a |
| 22 | Water (coolant) temperature sensor | Failed ECT sensor or wiring | Test sensor resistance against spec, replace if out of range. Cheap fix. |
| 24 | Intake air temperature sensor | Failed IAT sensor or wiring | Test IAT sensor; usually a $50 replacement |
| 31 | Boost pressure / MAP sensor | Failed MAP sensor, leaking vacuum line, or boost issue | Check vacuum lines first; test MAP signal at idle and under boost |
| 32 | Throttle position sensor (TPS) | Failed or out-of-spec TPS | Test TPS voltage sweep; if it spikes or drops out, replace |
| 34 | Turbocharger pressure signal | Boost out of expected range, turbo, wastegate, or sensor fault | Check wastegate operation, boost line for leaks, then sensor |
| 35 | Turbocharger / supercharger speed (rare on 1KZ-TE) | Sensor mismatch or wiring | Test wiring; not commonly seen |
| 42 | Vehicle speed sensor (VSS) | Failed VSS or wiring | Speedo also reads inaccurate, confirm both before replacing |
| 43 | Starter signal | Wiring fault or signal mismatch | Check starter relay and wiring to ECU |
| 51 | Switch condition (idle switch, neutral switch, A/C switch) | Idle switch out of adjustment, NSW failed, or A/C signal | Adjust idle switch on TPS, check neutral switch on auto trans |
| 89 | Glow plug controller (some markets) | Glow plug relay or controller fault | Test glow plug circuit; cold start will be poor if active |
The codes you'll actually see most often
After working on dozens of 1KZ-TEs, the codes that turn up in our workshop most often are 22, 24, 31, 32 and 51. Almost all of them are sensor failures, not engine failures.
Code 22 (water temperature) is the most common. The ECT sensor lives in the thermostat housing and sees a lot of heat over 25 years. When it fails, the ECU loses its primary input for fuel and timing maps, the engine still runs but you'll feel poor cold starts and rough running until warm-up. Cheap fix; budget NZ$50–$80 for the sensor.
Code 31 (MAP) often turns out to be a perished vacuum line rather than the sensor itself. Check the small rubber hose from the intake manifold to the MAP sensor before ordering parts. If the line is cracked or has gone hard, you've found your fault for the price of a metre of vacuum hose.
Code 51 (switch condition) is a catch-all for several inputs. The most frequent cause is the idle switch on the back of the TPS being out of adjustment. The fix is a 5-minute job with a 10mm spanner and a multimeter.
What's not in the code list
The 1KZ-TE flash-code system doesn't monitor everything. Things you have to diagnose by symptom rather than by code:
- Cracked head / blown head gasket, no code. Look for white smoke at idle, milky oil, coolant disappearing. Covered in our 3.0 turbo diesel guide.
- Injector wear, no code. Look for heavy black smoke at low load and a knocking noise.
- Injection pump timing drift, no code. Hard hot start, smoke under load, fuel knock.
- Timing belt stretch, no code. Loss of power, fuel economy drop. Replace on the 100,000 km interval regardless.
- Glow plug failure (individual), no code on most years. Hard cold start in winter.
A clean flash-code scan doesn't mean the engine is healthy, it means none of the sensors the ECU monitors are reporting a fault.
When the ECU resets itself
A few things will clear stored codes without you touching the EFI fuse:
- A flat or replaced battery
- The vehicle sitting unused with the battery disconnected
- Some workshops will clear codes during a service without telling you
If a Check Engine light returned after a battery change and the truck is running fine, do a code scan before assuming the worst, it's often a one-off fault that doesn't repeat.
Where to source diagnostic parts
For 3rd gen sensor replacements, the Genuine Toyota OEM Parts collection is the right place for the critical sensors (ECT, IAT, TPS). For 2nd gen, check the broader Hilux Surf Parts collection. Email us at campbell@surfsyndicate.co.nz if you need a part we haven't listed publicly.
Related reading
- Hilux Surf 3.0 Turbo Diesel: Mods, Failures & Service, the 1KZ-TE deep dive.
- Hilux Surf Oil Change Guide, service basics.
- KZN185 Hilux Surf Guide, platform overview.
FAQ
How do I read codes on a 1KZ-TE without a scan tool? Bridge terminals TC and CG (or TE1 and E1 on earlier connectors) on the engine-bay diagnostic connector with a jumper wire, turn the ignition to ON without starting, and watch the Check Engine light. The light will flash the two-digit codes, count the pulses with a 1.5-second gap between digits.
Does the 1KZ-TE have OBD-II? No. The 1KZ-TE uses Toyota's pre-OBD-II flash-code diagnostic system. A generic OBD-II scanner will not communicate with the ECU. The flash-code method is the factory diagnostic procedure.
What does code 32 mean on a 1KZ-TE? Code 32 is a Throttle Position Sensor (TPS) fault. Test the TPS voltage across its sweep range, if voltage spikes or drops out anywhere in the travel, replace the sensor. Also confirm the idle switch on the TPS is correctly adjusted before replacing the part.
Why is my Check Engine light staying on after I fixed the fault? Stored codes need to be cleared after the repair. Pull the EFI fuse (15A in the engine-bay fuse box) for 30 seconds, or disconnect the battery negative for 30 seconds. The light will go out and the ECU will re-scan on the next ignition cycle.
Can I clear codes by disconnecting the battery? Yes. 30 seconds is enough to drain residual ECU power. Note that this also clears learnt fuel trims, idle position, and electric window pinch-protect calibration, expect the truck to feel slightly different for the first few starts as it re-learns.
