2006 LX470 – P1440 / P1443 – Possible E1 (E6-1) Grounding Issue?
Vehicle: 2006 Lexus LX 470
Hey guys, I have been trying to solve a very annoying issue for a while now and I want to see if anyone can help/provide insight.
This problem originally started as with P0031 and P0051 codes. Both upstream A/F sensors were replaced, but the codes remained. Following the FSM diagnostics, both my mechanic and I independently arrived at the ECU as the suspected issue. I eventually swapped ECUs to no avail.
Later during a long drive, the truck simultaneously developed P1440 and P1443. Since then, the vehicle has experienced:
The intake manifold is currently removed due to cracked ports on the original manifold. While replacing the manifold, injector gaskets, injector vibration dampeners, and inspection of the SAIS system are being performed. SAIS pump and filter both appear mechanically functional. There is evidence that someone previously worked beneath the intake manifold, however the Filter and SAIS appears pristine.
P0031, P0051, P1440, and P1443 all are circuit low or circuit malfunction codes pointing toward opens/shorts in circuit.
Current Electrical Testing
Using the FSM procedure, I tested the SAIS VSV circuits:
The two VSV “ground/control” wires appear electrically connected to each other, but resistance back through E1 (E6-1) appears abnormally high implying an open/short on the return wires.
Current Theory
At this point I suspect the return ground wires from the Bank 1 & 2 VSV have a short due to the high resistance results showing no continuity.
I believe this short/open in the return wires of the VSV is what is causing P0031 and P0051 codes as they all share the same E1 (E6-1) return terminal at the ECU.
Main Question
Has anyone seen:
I will be testing continuity of all wires on the A/F sensors next to ensure there are no other wires not passing continuity check.
Any insight would be greatly appreciated.
Vehicle: 2006 Lexus LX 470
Hey guys, I have been trying to solve a very annoying issue for a while now and I want to see if anyone can help/provide insight.
This problem originally started as with P0031 and P0051 codes. Both upstream A/F sensors were replaced, but the codes remained. Following the FSM diagnostics, both my mechanic and I independently arrived at the ECU as the suspected issue. I eventually swapped ECUs to no avail.
Later during a long drive, the truck simultaneously developed P1440 and P1443. Since then, the vehicle has experienced:
- intermittent stalling immediately after startup
- vehicle starts better if ignition is left ON several seconds before cranking
- limp-mode style throttle limitation (~25% throttle), or throttle limited to 3kRPM
- harsh engagement into Drive and occasional harsh downshifts
- Complete throttle loss with headlights ON in extremely wet conditions
The intake manifold is currently removed due to cracked ports on the original manifold. While replacing the manifold, injector gaskets, injector vibration dampeners, and inspection of the SAIS system are being performed. SAIS pump and filter both appear mechanically functional. There is evidence that someone previously worked beneath the intake manifold, however the Filter and SAIS appears pristine.
P0031, P0051, P1440, and P1443 all are circuit low or circuit malfunction codes pointing toward opens/shorts in circuit.
Current Electrical Testing
Using the FSM procedure, I tested the SAIS VSV circuits:
| Test Location | Expected | Actual Result |
| VSV for Air Injection System (Bank 1) AIV1 (E8-27) → E1 (E6-1) | 9–14V IGN ON | 0.031V |
| VSV for Air Injection System (Bank 2) AIV2 (E8-26) → E1 (E6-1) | 9–14V IGN ON | 0.021V |
| Bank 1 VSV control wire continuity | Low resistance | ~315kΩ |
| Bank 2 VSV control wire continuity | Low resistance | ~315kΩ |
| Continuity between both VSV “ground” wires | Low resistance | ~0.2Ω |
| Resistance back through E1 (E6-1) toward ECU ground | Should be near ground potential | ~315kΩ |
Current Theory
At this point I suspect the return ground wires from the Bank 1 & 2 VSV have a short due to the high resistance results showing no continuity.
I believe this short/open in the return wires of the VSV is what is causing P0031 and P0051 codes as they all share the same E1 (E6-1) return terminal at the ECU.
Main Question
Has anyone seen:
- grounding failures, damaged splices, or high resistance conditions upstream of E1 (E6-1) on the 2UZ-FE?
- Could a short in the VSV return wiring heading to E1 (E6-1) terminal at ECU cause other systems to throw codes? I am wondering if they splice in to E1 line at the same location or share splices.
- P1440/P1443,
- throttle fail-safe behavior, or intermittent transmission/throttle abnormalities caused by SAIS VSV grounding issues or ECU return-path problems.
- Can I splice in a new wire upstream of the E1 (E6-1) return on ECU? I would run a new wire from VSV's throuh firewall and then splice them into the return wiring before the ECU.
I will be testing continuity of all wires on the A/F sensors next to ensure there are no other wires not passing continuity check.
Any insight would be greatly appreciated.