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JamesH, Auto Service Technician
Category: Car
Satisfied Customers: 663
Experience:  Auto Sercive Tech
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I have a engine code: p0171 fuel trim too lean (bank 1) what

Resolved Question:

i have a engine code: p0171 fuel trim too lean (bank 1) what are the steps to fix this problem?
Submitted: 8 years ago.
Category: Car
Expert:  JamesH replied 8 years ago.
HiCustomer Thank you for asking your question on JustAnswer. The other Experts and I are working on your answer. By the way, it would help us to know:
-What year is your Car?
-What make and model is your Car?
-How many miles are on your Car?
-What type of engine is in your Car?
-What have you already tried?

Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Customer: replied 8 years ago.
1998 toyota camry with 165,000 miles 3L
Expert:  JamesH replied 8 years ago.
There are alot of causes for this error. You need to check the intake connections and look for any air leaks. The next thing is to check the fuel pressure if those seem to be good there can be a problem with the engine temp sensor. This also can be a O2 sensor issue. I would start with the fuel pressure if there are no air leaks or a loose intake connections. I have attached how to check fuel pressure. let me know if you have any questions thanks!


(a) Check the battery positive voltage is above 12 V.
(b) Disconnect the negative (-) terminal cable from the battery.

(c) Purchase the new No.1 fuel pipe and take out the fuel tube connector from its pipe.
Part No. 23801-20040

(d) Remove the fuel hose clamp.

(e) Disconnect the No.1 fuel pipe (fuel tube connector) from the fuel filter outlet.


  • Perform disconnecting operations of the fuel tube connector (quick type) after observing the precautions.
  • As there is retained pressure in the fuel pipe line, prevent it from splashing inside the engine compartment.

(f) Install SST (pressure gauge) as shown in the illustration by using SST and fuel tube connector. SST(NNN) NNN-NNNN(NNN) NNN-NNNN(NNN) NNN-NNNN/td>
(g) Wipe off any splattered gasoline.
(h) Reconnect the negative (-) terminal cable to the battery.
(i) Connect the TOYOTA hand held tester to the DLC3.
(1) Turn the ignition switch ON and TOYOTA hand-held tester main switch ON.

NOTICE: Do not start the engine.

(2) Select the active test mode on the TOYOTA hand-held tester.
(3) Please refer to the TOYOTA hand-held tester operator's manual for further details.
(j) Measure the fuel pressure.
Fuel pressure: 301 - 347 kPa (3.1 - 3.5 kgf/, 44 - 50 psi)

If pressure is high, replace the fuel pressure regulator.
If pressure is low, check these parts:

  • Fuel hoses and connections
  • Fuel pump
  • Fuel filter
  • Fuel pressure regulator
(k) Disconnect the TOYOTA hand-held tester from the DLC3.
(l) Start the engine.
(m) Measure the fuel pressure at idle.
Fuel pressure: 301 - 347 kPa (3.1 - 3.5 kgf/, 44 - 50 psi)
(n) Stop the engine.
(o) Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.
Fuel pressure: 147 kPa (1.5 kgf/, 21 psi) or more

If pressure is not as specified, check the fuel pump, pressure regulator and/or injectors.

(p) After checking fuel pressure, disconnect the negative (-) terminal cable from the battery and carefully remove the SST and fuel tube connector to prevent gasoline from splashing. SST(NNN) NNN-NNNN(NNN) NNN-NNNN(NNN) NNN-NNNN/td>

(q) Reconnect the No.1 fuel pipe (fuel tube connector).

CAUTION: Perform connecting operations of the fuel tube connector (quick type) afier observing the precautions.

(r) Surely install the fuel hose clamp to the fuel filter with "click" sound.
(s) After installing the clamp, check that the clamp is fixed by pulling up the clamp.
(t) Reconnect the negative (-) terminal cable to the battery.
(u) Check for fuel leaks.


Customer: replied 8 years ago.
the images won't open
Expert:  JamesH replied 8 years ago.
it maybe a issue with your browser it happens in the newer IE try using firefox which is a free browser you can download from search if you still cant let me know.. Thanks
Customer: replied 8 years ago.
i tried firefox and still can't open pics
Expert:  JamesH replied 8 years ago.
Sorry I was away and when I am away the pictures are blank try again with firefox..
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