Only idles with TPS unplugged

Tiny
SRRAVE3
  • MEMBER
  • 1996 BUICK REGAL
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 220 MILES
Grand sport model only stays idle when you unplug the TPS. I have a variable voltage without drop out in voltage. The ground circuit is clean. It is getting 5 volts and has been replaced. I checked for worn wires near and around the crank sensor and checked for other faults. After a bunch of tries cranking over I just unplug the TPS connector and it idles around 1,100 rpm's and is stable. When running I connect TPS back up and it goes straight into a fall in rpm's and shuts off. So confused if I get good ground and constant voltage for my variable read out along with good read out on my voltage pot measurement? I did read the article about a small dropout in voltage in the sensor. But have the recommended voltage. I have a Zurich zr8 from Harbor Freight. It gave me a code of p0122. I suspect the PCM is having trouble but, I have a dvm and know how to use it. I did notice in live data it takes 25* of advance (timing) when holding gas down to achieve 1,250 rpm's Buick enhanced data shows multiple sensor circuits with low voltage showing. Here is the freeze from holding down gas to get stated rpm:
Fuel Sys 1 OL
Fuel Sys 2 N/A
Calc Load 9.41 %
ECT 163.40 °F
STFT B1 -0.78 %
LTFT B1 -7.81 %
MAP 19.79 inHg
Eng RPM 1043.50
Veh Speed 0.00 mph
MAF 2.11 lb/min
TPS -- %
Monday, July 30th, 2018 AT 8:02 PM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

With the TPS hooked up, what is the voltage of the TPS at idle?
What is the voltage at wide open throttle?

Lets start with those readings.

Roy

CIRCUIT DESCRIPTION

The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from less than 1 volt at closed throttle to about 4 volts at Wide Open Throttle (WOT). The TP signal is one of the most important inputs used by the Powertrain Control Module (PCM) for fuel control and most of the PCM-controlled outputs. The PCM monitors throttle position and compares actual throttle position from the TP sensor to a predicted TP value calculated from engine speed. If the PCM detects an excessively low TP sensor signal voltage, DTC P0122 will be set.

CONDITIONS FOR SETTING THE DTC

The ignition is ON.

TP sensor signal voltage is less than 0.16 volt.

Above conditions are present for longer than 1 second.

ACTION TAKEN WHEN THE DTC SETS

The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the first trip in which the diagnostic test has been run and failed.

The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC

The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

DIAGNOSTIC AIDS

Check for the following conditions:

Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the throttle position display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the fault.

If DTC P0122 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing DTC P1122 Diagnosis may isolate the cause of the fault.

TEST DESCRIPTION

Number(s) below refer to the Step number(s) on the Diagnostic Table:

12. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement(Programming.
Was this
answer
helpful?
Yes
No
Tuesday, July 31st, 2018 AT 3:55 AM

Please login or register to post a reply.

Sponsored links