2013 scion FRS intermittent p1235
 

Hello, new to the forum and have no idea how to use the threads to attach this to the applicable thread...... how ever I have an intermittent p1235 that only comes at idle. it doesn't seem to affect driveability at all, i do notice when coming to a stop the rpms drop a bit and the car shakes and the rpms then rise to a normal idle.

I have pulled the fuel pump (low pressure pump) out of the car put it on a bench and confirmed it has good flow without the filter and with the filter attached to the pump, I confirmed the pump is doing its job well, not sure if maybe the fuel pump driver module or control module what ever you call it, maybe thats a cause or if its the dreaded hpfp. like i mentioned it only occurs at idle and if I blip the throttle at idle the rpms drop the car stumbles a bit than comes back up to a normal idle.

car is COMPLETELY stock minus a sound system. and a bigger agm battery/big3 upgrade only has 73 thousand km on the car

DTC: P1235

DTC detection condition: The diagnostic signal from the injector driver (EDU) does not change when the high pressure fuel pump is driven (open/short condition in the high pressure fuel pump circuit)
(1 trips detection logic)

Suspected parts:
• Open or short condition in fuel pump (high pressure side) circuit
• High pressure fuel pump
• Injector driver (EDU)
• ECM

INSPECTION STEPS
NOTE:
Read the freeze frame data using the SSM3. A part of the engine running conditions under which the engine trouble occurred is recorded in the freeze frame data, which is useful for troubleshooting.
1. Fuel pump ASSY unit inspection (high-pressure side)

(1) Check the fuel pump ASSY (high-pressure side).
NG
>Replacement of fuel pump ASSY

OK▼

2. Check wiring harness and connector (injector driver - fuel pump ASSY (high-pressure side))

(1) Disconnect injector driver connectors.
(2) Disconnect the fuel pump ASSY (high-pressure side) connectors.
(3) Measure the resistance between the terminals.
Resistance (open circuit check)
Inspection terminals
Inspection conditions
Standard value
C2-3 (FP-) - C29-2
Always
Less than 1 Ω
C2-4 (FP+) - C29-1
Always
Less than 1 Ω
Resistance (short circuit check)
Inspection terminals
Inspection conditions
Standard value
C2-3 (FP-) and C29-2 - other terminals and chassis ground
Always
10 k Ω or more
C2-4 (FP+) and C29-1 - other terminals and chassis ground
Always
10 k Ω or more
NG
>Repair or replacement of wiring harness or connector

OK▼

3. Check wiring harness and connector (engine control computer - injector driver)

(1) Disconnect the connector for the engine control computer.
(2) Disconnect injector driver connectors.
(3) Measure the resistance between the terminals. (Refer to for the terminal arrangement)
Resistance (open circuit check)
Inspection terminals
Inspection conditions
Standard value
A34-32 (FPD) - C1-8 (FPD)
Always
Less than 1 Ω
A34-13 (FPF) - C1-7 (FPF)
Always
Less than 1 Ω
Resistance (short circuit check)
Inspection terminals
Inspection conditions
Standard value
A34-32 (FPD) and C1-8 (FPD) - other terminals and chassis ground
Always
10 k Ω or more
A34-13 (FPF) and C1-7 (FPF) - other terminals and chassis ground
Always
10 k Ω or more
NG
>Repair or replacement of wiring harness or connector

OK▼

4. Engine control computer check (FPD output)

NOTE:
For the inspection procedure and precautions for wiring harnesses and connectors, refer to .
(1) Using an oscilloscope, check the waveform. (Refer to for the terminal arrangement)
Item
Contents
Measuring terminal
A34-32 (FPD) - chassis ground
Equipment setting
2 V/DIV, 20 ms/DIV
Measuring condition
During idling
Captions in illustration
*a
Connector connected
(engine control computer)
*b
Normal waveform at FPD terminal
Criteria : Normal waveform is output.
NOTE:
If DTCs are output after the engine is started from IG OFF state, the fail-safe mode takes effect. Therefore the FPD waveform is output only immediately after start-up.
NG
> Go to Step 6.

OK▼

5. Engine control computer check (FPF output)

(1) Using an oscilloscope, check the waveform. (Refer to for the terminal arrangement)
Captions in illustration
*a
Connector connected
(engine control computer)
*b
Normal waveform at FPD and FPF terminals
*c
FPF waveform, NG waveform 1
*d
FPF waveform, NG waveform 2
Item
Contents
Measuring terminal
CH1: A34-32 (FPD) - chassis ground
CH2: A34-13 (FPF) - chassis ground
Equipment setting
2 V/DIV, 20 ms/DIV
Measuring condition
During idling
(2) When FPF terminal waveform is NG waveform 1, stop the engine, disconnect the injector driver connectors, and check the change in FPF waveform during cranking.
Result
FPD waveform
FPF waveform
Check performed when NG waveform 1 results
(FPF waveform does not change from GND when ignition is switched from OFF→ON)
NG waveform 2
Change takes place
(FPF waveform rises from GND when ignition is switched from OFF→ON)
B

OK
NG waveform 2
-
B
>Replacement of injector driver

A▼
Replacement of the engine control computer

6. Engine control computer check (FPD output)

(1) Disconnect injector driver connectors.
(2) Using an oscilloscope, check the waveform. (Refer to for the terminal arrangement)
Captions in illustration
*a
Connector connected
(engine control computer)
*b
Normal waveform at FPD terminal
Item
Contents
Measuring terminal
A34-32 (FPD) - chassis ground
Equipment setting
2 V/DIV, 20 ms/DIV
Measuring condition
When cranking
Result : Normal waveform is output.
NG
>Replacement of the engine control computer

OK▼
Replacement of injector driver