Research note
98 5VZ-FE engine-bay connections OTHER than II1/II2/II3 and the ECM
Source: EWD319U (TIS PDFs in manuals/1998-4runner/ewd/). "p.NN" means the printed EWD page number. Every page cited was rendered and read as an image.
Renders are in scratchpad/renderE/.
Key pages: Connectors p.36–37 (engine-bay joints and grounds), p.40–41 (cowl joints), Component Locations p.26–27, Relay Locations p.18–23,
Power Source p.58/60, Charging p.70–71, Engine Control p.74–79, ECT p.120–121, 4WD w/o 2-4 SW p.164–165, A/C p.235, Ground Points p.240–243,
Overall EWD sheet 1 (Starting/Charging, PDF page index 3) and sheet 2 (Ignition, PDF index 4).
Headline
- On the 98 the engine wire touches only 6 things besides the ECM: II1/II2/II3 (cowl), EB1 (knock-sensor wire), EC1 (coolant-temp sensor wire),
ED1 (front-diff ADD switch wire), the EC ground eyelets, and the component plugs on the engine and trans themselves.
No engine-wire circuit goes directly to the engine-room R/B, the battery, or the engine room main wire (p.36–37, 74–77, 79).
Every R/B fuse or relay output reaches the engine wire by going main wire → IG1 → cowl wire → II1/II3.
So the conversion table's II-joint list already covers all the power and control feeds.
- The alternator and starter-solenoid plugs are NOT on the engine wire. They're on a separate small harness, the "Engine No.2 Wire".
It joins the engine room main wire at EA1 (gray, 4-pin, near the engine room R/B) (p.37, p.70–71, Overall sheet 1).
If the donor came without the Engine No.2 wire, plan to build those 4 circuits from scratch.
Check the donor: look for a gray 4-pin plug near the old R/B location, feeding a gray 3-pin plug at the alternator and a black 1-pin plug at the starter.
- The EFI relay, starter relay, circuit opening relay (COR) and every fuse are gone with the R/B and main wire.
The COR (C6) is on the cowl wire at the driver-side J/B, not on the engine wire (p.19, p.74).
- No A/C clutch relay exists on the 98. The A/C amplifier's MGC output drives the clutch coil directly (p.235).
Q1. Every joint on the engine wire (other than II1/II2/II3 + ECM)
| Joint | Joins | Location | Pins / circuits | Swap |
|---|---|---|---|---|
| EB1 (dark gray / gray, 3-pin) | Engine wire ↔ Sensor wire (knock sensors under the intake plenum) | Front of RH cylinder head cover (p.36–37) | 1 B = KNK1 (E10-15) shielded; 2 GR = KNK2 (E10-14) shielded; 3 BR = shield drain, sensor-side splice E2 → engine-side splice E1 → I11 → EC (p.76) | Re-mate. It goes with the engine. |
| EC1 (gray, 2-pin) | Engine wire ↔ Water temp sensor wire (ECT sensor E3) | Front of RH cylinder head cover (p.36–37) | 1 BR-B = E2 sensor ground; 2 G (engine side) / G-Y (sensor side) = THW (E10-20) (p.75, p.120) | Re-mate. |
| ED1 (gray, 2-pin) | Engine wire ↔ Front differential wire | Near the front differential (p.37, p.165) | 1 G-R, 2 G-B = ADD indicator switch A10 (or short pin on trucks without ADD). G-R → I11 → II3-17 (ADD control relay); G-B → I11 → II3-9 + ECM 4WD (E9-1) (p.164) | Drop unless you want the 88's 4WD light from the ADD switch. The 88 front diff has its own switch. |
| EC ground eyelet(s) | Engine wire → intake manifold, left | p.36, p.79, Overall sheet 2 "Intake manifold left (5VZ-FE)" | Covered in Q4 | Keep and bolt down. |
| EA1 (gray, 4-pin) | Engine No.2 wire ↔ engine room main wire. Not the engine wire. | Near the engine room R/B (p.37, p.71) | 1 R-L = alt IG; 2 Y-G = alt L; 3 B-W = starter terminal 50; 4 W = alt S (p.70, Overall sheet 1) | The main-wire side is gone. See Q2/Q3. |
Not found on the 5VZ engine wire: IE-, EA- or other E-series joints, and the R/B plugs 1A–1K / 2 / 3A–3E.
1A–1K plug into the driver-side J/B (cowl and main wire, p.22). 3A–3E are on the center J/B (cowl). "2" is the engine-room R/B, wired by the engine room main wire.
The engine wire's own splices are I11 (in-cabin run) and E1 (engine bay) (p.79).
What the swap must reconnect from the lost R/B and main wire (all via the II joints already mapped)
| 98 source (lost) | 98 path | Reaches engine wire at | 88 replacement |
|---|---|---|---|
| EFI relay (R/B "2"). Coil: 7.5A IGN (J/B 1J-8, GR-B). Contact: 15A EFI. Coil ground W-B → J1/J2 → EB | pin 3 W-L → IG1-1 → cowl splices I5/I10 | II3-16 W-L (MAF +B, IAC, VSVs, O2 heaters, DLC1 +B) and E12-23 W-L (ECM +B) (p.74–76) | 88 EFI relay output (N5-12 B-Y) |
| 15A EFI constant | L-R → IG1-7 → cowl | E12-14 BATT (p.74–75, p.120) | 88 constant feed (N5-4 G-Y) |
| 7.5A STA (fed by ignition ST2, G-B, A/T only) | B → IG1-22 → II3-2 → ECM NSW E9-14 + P/N switch P1-6 (p.75, p.120, Overall sheet 1) | II3-2 | See Q6 (NSW) |
| Starter relay (R/B). Coil fed through the A/T P/N switch: P1-5 B-W → II1-6 → cowl → IG1-6 → relay pin 1; coil ground W-B → EB. Output pin 3 B-W → EA1-3 → starter S1 | II1-6 also feeds ECM STA E9-13 (p.74–75, Overall sheet 1) | II1-6 B-W | 88 starter circuit (N5-9). Starter 50 wire: Q3 |
| COR C6 (cowl wire, behind the driver-side J/B). Coil: +B from I5 (EFI relay out), ground through FC. Contact: I5 → 3A → IE2-16 → pump (p.19, p.74) | FC G-Y → II3-26 → ECM E10-18 | II3-26 | 88 COR (N5-8) |
| 10A STOP | G-Y → IG1-14 → stop switch S4 → G-W → 3E → E12-24 (p.74, p.120) | E12-24 | 88 stop switch (N5-5) |
| 7.5A OBD | V → IG1-3 → DLC3 pin 16 (p.77) | cowl only, never the engine wire | New fused 12 V at DLC3-16 (already in the table) |
| 7.5A IGN to EFI relay coil | relay box only | — | 88 EFI relay |
| IG2 (ignition switch IG2 B-R) | I3 → IG1-5 → II3-8 | II3-8 | N5-15 |
Q2. Charging (5VZ-FE): p.70–71, Overall sheet 1
Generator plug G1 (A): gray, 3-pin on the Engine No.2 wire. G2 (B): ring-terminal stud for B (p.71).
| Alt terminal | Pin | 98 color | Harness | 98 source | Swap must supply |
|---|---|---|---|---|---|
| B (output) | G2-1 stud | W | Main wire / battery (100A ALT fuse 2 → stud direct; p.70, R/B layout p.20) | 100A ALT fusible block in the R/B, fed from battery + | A fused heavy cable from the 88 battery/ALT link to the stud. Size the link to the 5VZ alternator's output: 98 = 100A. Check what the 88's ALT link and wire are rated for (UNVERIFIED). |
| IG | G1-2 | R-L | Engine No.2 wire → EA1-1 → main wire | 10A GAUGE (J/B 1J-1) → J1/J2 junction connectors → EA1-1 | Ignition-switched 12 V (the 88 alternator IG wire) |
| L | G1-1 | Y-G | Engine No.2 wire → EA1-2 → main wire → J5 → IG1-16 → cowl → charge warning light C11-1 (B-side); lamp fed from 7.5A IGN (1D-1, GR-B). Also branches to the DRL relay (Canada) | Lamp-side ground path | 88 charge-lamp wire. Lamp in series from IG to L. Without the lamp/L circuit the IC regulator may not excite (Toyota IC-regulator behavior, not stated in EWD) |
| S (battery sense) | G1-3 | W | Engine No.2 wire → EA1-4 → main wire → 7.5A ALT-S (fed from the 100A ALT output side) | Constant 12 V, fused 7.5A | Constant-battery 7.5A feed. If the 88 alt plug has no S wire, add one. Some Toyota IC regulators charge from internal sensing with S open, but don't count on it (UNVERIFIED) |
| Ground | case | — | Through the alternator bracket and block | — | Good block-to-battery-negative ground |
Service hint (p.71): G2(B)-ground 13.9–15.1 V at 2000 rpm and 25 °C. G1(A)-1 (L) 0–4 V at key ON, engine off.
Swap action: if the donor's Engine No.2 wire is present, cut its EA1 plug and splice those 4 wires to the 88 sources above. If it's absent, build a 3-pin pigtail for G1.
The 88 3VZ alternator plug pinout and its ALT fusible-link rating are UNVERIFIED (needs EWD040U).
Q3. Starter: Overall sheet 1, p.27, p.74
- Starter S1 (A): black, 1-pin = terminal 50, B-W. Path: starter relay pin 3 (R/B) → B-W → EA1-3 → Engine No.2 wire → S1.
- Starter S2 (B): ring terminal = terminal 30, B-L battery cable (5VZ-FE) straight from battery + (B on the 3RZ).
- The engine wire carries no starter wire. Its only start-related wires are signals: ECM STA (E9-13, B-W, via II1-6) and the A/T P/N switch P1.
- Swap: run the 88 battery cable to S2. Run the 88 starter-relay/clutch-switch output (N5-9 side, or the 88 starter-50 wire) to S1.
This matches the existing table note "run a new wire from N5-9 to starter terminal 50". Use the 88 starter relay and clutch start switch.
Q4. Grounds: p.36, p.79, p.240–243, Overall sheets 1–2
| Ground | Where it bolts | Who uses it | On user's engine wire? | Swap |
|---|---|---|---|---|
| EC | Intake manifold, left (Overall sheet 2; p.79) | ECM E1 (E11-16), E01 (E9-34), E02 (E9-33), E03 (E9-28, via I11); igniter GND (I2-3); noise filter N1-2; O2 sensors bank 1 S1/S2 (E1 lead, via I11); DLC1 E1; SIL shield (II3-24 via I18/I11); DLC3 SG (cowl side BR-R → II3-18) (p.77, p.242) | YES. The BR eyelets are engine-wire terminals | Keep. Bolt to the 5VZ left intake manifold stud. Make sure the engine block has a heavy strap to the 88 battery negative and to the body. ECM and igniter ground through this eyelet. |
| EB | Front left fender | Starter relay, EFI relay, heater relay, PWR outlet relay (direct); via J1/J2: front parking/turn lights, ABS relay, brake fluid level switch, ADD VSVs V4/V5, EFI relay (p.240, p.74, p.164) | No. Main wire / R/B | Not needed. The 88 relays use their own grounds |
| EA | Front right fender | ABS actuator (p.240, Overall) | No | — |
| IE | Cowl side panel LH | Fuel pump (via J12/IE2-17), buckle, meter, etc. (p.240) | No (cowl/floor) | 88 pump has its own ground |
| IF | Cowl side panel RH | Transfer switches D4/D5/D3 (W-B → I11 → II3-10 → 3E → J9 → IF), DLC3 CG pin 4 (p.164, p.241, p.77) | Only via II3-10 | Drop (98 transfer switches); DLC3-4 → body ground (already in table) |
| E2 sensor ground | — | Signal return from TPS, MAF, ECT, vapor sensor, ATF temp (BR-B) to ECM E10-22 / E11-7. Floats on the ECM, not chassis (p.75) | Internal | Don't ground it |
| Component self-grounds | case | A/C clutch A2, knock sensors K2/K3, PS switch P22, oil switch O1, E2 trans solenoid (p.75–76, 120, 235) | — | They need a good engine/trans-to-battery ground |
Must recreate: only the EC eyelet (it comes with the harness, bolt it on) plus a solid engine-block ↔ battery-negative ↔ body/frame strap.
The battery/engine ground cables aren't drawn in EWD319U beyond the battery symbol, so the strap location is not in these pages.
Q5. COR, EFI relay, A/C clutch relay
- Circuit opening relay C6: cowl wire, lost. It's on the instrument-panel side, at the driver-side J/B / lower finish panel ("Circuit Opening Relay", Relay Locations p.19).
The p.74 drawing ties its +B to cowl splice I5 and its contact to 3A / IE2-16 (floor wire to the pump).
Its ground side is J12, which is a floor/cowl junction connector (p.32 ref, p.240), not on the engine wire.
The engine wire carries only the FC control wire, II3-26 G-Y. The swap uses the 88's COR (already planned).
- EFI relay: R/B, lost (p.20, p.74). Only its output (W-L) reaches the engine wire, via II3-16 and E12-23.
- Starter relay: R/B, lost (p.20).
- A/C magnetic clutch relay: none on the 98. A/C amplifier A12 pin 9 MGC (B-Y) → IJ1-2 → cowl LG-B → II3-25 → engine wire → clutch A2-1, which grounds through the compressor body (p.235).
The ECM sees A/C on via AC1/ACT (E12-16/E12-5).
If the 88 A/C uses a clutch relay or a different control, how it would drive II3-25 is UNVERIFIED (needs EWD040U).
- 15A A/C fuse, 50A HEATER, HEATER relay: R/B, lost. They feed only the A/C/blower circuits, not the engine wire (p.58, p.236).
Q6. Other things on the engine wire that will dangle (no 98 R/B, main wire or A/T)
- A/T park/neutral switch P1 plug (on the transmission; engine wire). Per Overall sheet 1: II3-2 B (from STA fuse) → P1-6 → (P or N) → P1-5 B-W → II1-6 → starter relay coil. The ECM STA branch (E9-13) sits on that B-W line.
P1-4/7 = A/T P indicator (II3-20 B-Y, II3-1 L-Y) (p.164–165).
- Don't jumper the P/N plug pins 5–6. That would tie NSW (E9-14) straight to the STA line. When it isn't cranking, the STA line is pulled toward ground through the starter-relay coil, so NSW would read "P/N" all the time and could set P1780 (RM580U DI-253).
Leave P1 unplugged and taped, so NSW reads "in gear" (consistent with the table's "leave NSW open").
- Whether there is an internal engine-wire splice between P1-5, E9-13 and II1-6: Overall sheet 1 shows the ECM-STA branch on the P1-5/II1-6 line.
Check with an ohmmeter on the donor harness before relying on it (UNVERIFIED by continuity).
- A/T solenoid plug E2 (S1/S2/SL), ATF temp sensor A3, VSS V3 (SP2) on the A340 (p.120). These dangle with the R150 and set the A/T DTCs already noted in TODO.
- Transfer detection switches D3 (4WD), D4 (L4), D5 (neutral) on the 98 transfer, ground W-B via II3-10 (p.121, p.164). They dangle; the 88 transfer has its own 4WD switch.
- ED1 front-diff ADD switch (above). Optional.
- Oil pressure switch O1 (II3-22 G-W) and water temp sender W2 (II3-21 Y-R) (p.27; table already covers them).
- A/C clutch A2 (II3-25). Optional.
- Power steering pressure switch P22 (P, ECM PSW E9-31, self-grounded) (p.76). Plug it into the 5VZ PS pump if fitted. Otherwise it stays open = no PS idle-up (no DTC expected; UNVERIFIED).
- DLC1 (D1), engine-bay diag box (p.76–77, p.26). Fed from the engine-wire W-L splice and igniter EXT. TC/OP3/ABS/SRS pins come via II1/II3 and drop. It stays usable for TE1 only if you keep it.
- Noise filter N1 (B-R IG2 → EC, Overall sheet 2). Self-contained. Keep.
- VSV (2WD/4WD ADD) V4/V5 are NOT on the engine wire. Main wire, IG1-23/24, EB ground (p.164). Nothing to do.
- The Engine No.2 wire / EA1 (alternator + starter 50) if it came with the donor: its EA1 plug dangles. Repurpose it as in Q2/Q3.
- II-joint wires already marked Drop (see
ii-joint-connector-map.md).
Corrections / additions for the project files
- Add to the conversion table: alternator IG / L / S and starter-50 come from EA1 (Engine No.2 wire), not the engine wire. Four 88 feeds are needed: IG (switched), L (charge lamp), S (fused constant), 50 (88 starter circuit). Plus the B cable and battery cable.
- Add EB1, EC1 (re-mate) and EC eyelet (bolt to left intake manifold) to the checklist.
- COR placement confirmed: cowl, lost. The 88 COR stays.
- Add the P/N plug warning (don't jumper, leave open) next to the NSW section.