Two SR20 trigger styles
How your SR20 is triggered depends mostly on its ignition. Naturally aspirated SR20s are commonly distributor engines. Direct-fire engines, which are mostly the turbo versions, use a separate crank angle sensor (CAS) on the end of the cam instead.
Both produce the same two signals:
- 4x: four pulses per engine cycle. Nissan calls this the "180-degree" signal. It goes to Trigger+.
- 360x: Nissan's "1 degree" signal. It goes to Home+. Despite the name, there are 360 slots spread over a full 720 crank degree cycle, so each slot is actually two crank degrees.
Keeping that naming straight saves confusion when you're comparing a factory service manual to Haltech's trigger labels.
CAS wiring (S13, S14, S15)
| CAS pin | Signal | Connect to (Haltech) |
|---|---|---|
| 1 | Signal ground | Signal Ground, blue wire in the Trigger 4-core |
| 2 | Switched 12V | 12V+, red wire in the Trigger 4-core |
| 3 | 360x | Home+, yellow wire in the Home 4-core |
| 4 | 4x | Trigger+, yellow wire in the Trigger 4-core |
Distributor wiring
SR20 distributors come with either an internal coil or an external one. The table below is for the internal coil type, which uses an 8-pin connector.
| Dist. pin | Signal | Connect to (Haltech) |
|---|---|---|
| 1 | Ignition trigger from ECU | Ignition Output 1 |
| 2 | Power ground (to cylinder head) | Not connected to the ECU |
| 3 | 360x | Home+, yellow in the Home 4-core |
| 4 | 4x | Trigger+, yellow in the Trigger 4-core |
| 5 | 12V+ | 12V+, red in the Trigger 4-core |
| 6 | Signal ground | Signal Ground, blue in the Trigger 4-core |
| 7 | Switched 12V for the coil | Not connected to the ECU |
| 8 | Unused | Not connected |
The one-cable shortcut
When the CAS or distributor has a dual pickup, its two outputs share one power feed and one ground. Haltech's harness gives you two 4-core shielded cables, one for Trigger and one for Home, which means running two cables to the CAS or distributor when one would do. Because the Trigger cable's green Trigger- wire goes unused with this type of sensor, you can move that wire to the Home+ pin at the ECU plug. The Trigger 4-core then carries 12V+, ground, Trigger+ and Home+ all together, and the Home cable isn't needed at the sensor.
Unlocking the main connector is the same on every Elite: press the large white tab until it clicks, and the two small white locking tabs on the other side pop up. Relock by pressing those two tabs back down.
| ECU | Connector | Remove yellow Home+ from | Move green Trigger- from | Into |
|---|---|---|---|---|
| Elite 550 / 750 / 950 | Main connector | Pin 32 | Pin 33 | Pin 32 |
| Elite 1000 / 1500 / 2000 / 2500 | 26-pin main connector | Pin 2 | Pin 5 | Pin 2 |
- Unplug the connector from the ECU and unlock it.
- Pull the yellow Home+ wire out of its pin and insulate the end. It won't be used.
- Move the green Trigger- wire into the Home+ cavity. Push it fully home: from the pin face, the terminal should sit flush with its neighbors.
- Relock the connector and label the green wire as Home+ at the sensor end so the next person isn't caught out.
A terminal that isn't fully seated can back out when you plug the connector in, and the engine will show no Home signal. Tug-test each moved wire gently before relocking.
Trigger settings in software
Once wired, the trigger has to be configured in software for the SR20 pattern, with separate settings for direct-fire CAS engines and distributor engines. Haltech's reference screenshots show the values for each. Base maps and plug-in ECUs such as the Elite 1500 S13/180SX SR20DET and Nexus S3 S13 SR20 plug-n-play kit arrive set up for this engine. On a universal install, always confirm with a timing light after setup. Our calibrating ignition timing guide covers that step.
Need this diagram? Ask us and we'll send it over with advice for your build.
Troubleshooting
| Symptom | Usually |
|---|---|
| No RPM while cranking | No 12V at the sensor, or Trigger+ and Home+ swapped |
| RPM shows but no Home/sync | Moved wire not fully seated, or the old Home+ still connected |
| Timing drifts or jumps | Shielding not grounded correctly or a worn CAS; see trigger wiring |
For the rest of the engine, see our SR20 engine overview.
