Figured I'd throw this one up here and see if any other mechanics have run into this code before.


Customer came in with a check engine light complaint. Confirmed codes P1283 and P1800. MAF and B2S1 AFR sensor were replaced by customer. Unknown brand of AFR sensor more than likely Bosch.

Visual inspection showed rotted PCV hose. Replaced PCV hose.

A/F Alpha on B2 showed roughly 125%
B2S1 Voltage showed sub 1.4v
Rear O2s had good range and responded to changes (creating a vacuum leak/adding fuel). Engine vacuum roughly 20inHg
MAF passed VE check
Other sensors ECT, IAT, MAP, BARO looked OK

Cleared the code and self learn. Within a few drive cycles P1283 came back.

Smoke tested the intake (cold). No visible leak. Sprayed with soapy water confirmed no vacuum leaks.

Per TSB NTB04-019A checked B2 catalytic converter for loose/missing bolts. All bolts secure and present.

Smoke tested the exhaust. No exhaust leaks found.

Per TSB NTB04-090 ohmed the injectors. All injectors had roughly 14ohms @ 157*F.

At this point I opted to replace the AFR sensor with an NTK (OE brand).

Replaced the AFR sensor, cleared the code and self learn and drove for monitors. The O2 monitor took a few drive cycles to pass so something seemingly was wrong, but scan data showed A/F alpha right around 105% and sensor voltage at around 1.5v. Eventually it passed the monitor and got it's inspection sticker. Mode $6 confirmed test passed with some margin.

Given the presence of TSBs I would think that this code (P1283) isn't that uncommon. Though this is the only time I've ever run into the code.

My Question

Has anyone ever ran into this issue before? And if so what was the cause/final solution?

  • I haven't personally seen it, but would say you diagnosed it right down the line ... Great write-up, btw. Feb 9, 2016 at 12:13
  • yes, nice write-up. Would like to hear someone chime in with a good response as well. Feb 10, 2016 at 0:12
  • I wonder if the P1800 is the true root cause here, with the lean AFR code a symptom of it. I can't make sense of how the "power valve" is altering the intake tract conditions based on the link, but am mentioning it since you went after the other code and not this one
    – Zaid
    Feb 13, 2016 at 7:26

1 Answer 1


That P1800 may be key

This is an elaboration of my comment on how P1800 can explain your observations.

Code Details

P1800 Nissan - Variable Intake Air System Control Solenoid Valve Circuit

When the engine is running at low or medium speed, the power valve is fully closed. Under this condition, the effective suction port length is equivalent to the total length of the intake manifold collector's suction port including the intake valve. This long suction port provides increased air intake which results in improved suction efficiency and higher torque generation.

The surge tank and one-way valve are provided. When engine is running at high speed, the Engine Control Module (ECM) sends the signal to the Variable Intake Air System (VIAS) control solenoid valve. This signal introduces the intake manifold vacuum into the power valve actuator and therefore opens the power valve to two suction passages together in the collector.

Under this condition, the effective port length is equivalent to the length of the suction port provided independently for each cylinder. This shortened port length results in enhanced engine output with reduced suction resistance under high speeds.

My Interpretation

This car has a dual air-intake setup, and the "power valve" is a vacuum-operated means to select which intake tract the air flows through.

Variable Length Intake

Based on the description above, the shorter runner is intended for high RPM conditions, the longer one for low/medium RPM conditions. There is no "in-between" condition where air is being fed in from both runners.

The lean AFR could be the result of a mismatch between what intake runner the engine management is expecting and what is actually being used.

It may also explain why a smoke test returned negative for leaks.

  • The p1800 was seemingly intermittent and never returned after the first test drive. I don't think there was any real correlation between the codes. While butterfly valves in the manifold can go bad. I've only seen it on ones with plastic valves, like on Fords. Usually it's a failure of the vacuum solenoid or vacuum lines/tank/diaphragm on Nissans. On this particular car the customer had done some of his own work and may have inadvertently started the car with the plug or vacuum line disconnected.
    – Ben
    Feb 13, 2016 at 21:59

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